yesterday i accidentally ran test code related to this issue and i found out that the issue is fixed. i think i did the test a week or so back and the issue was still there.
here is the output from my log. the messages are sorted by the message type rather than by the arrival time to make it more readable.
# i use v178, but i doubt that is really related, just keeping it here for transparency, other initialization messages omitted
INFO: Sending message: V100API_HEADER[2023-09-13 05:32:58.384]: API-----v178
INFO: Received message: SERVER_VERSION[2023-09-13 05:32:58.389]: ---178-20230913 07:32:57 CET-
INFO: Sending message: START_API[2023-09-13 05:32:58.390]: ----71-2-1111--
# here is a request for 5s midpoint realtime bars, there are values even with 6 decimal places, so half a tick (that is exactly what it should be for midpoint data)
INFO: Sending message: REQUEST_REALTIME_BARS[2023-09-13 05:32:58.439]: ---350-3-1--EUR-CASH-----IDEALPRO--USD---5-MIDPOINT-0--
INFO: Received message: REAL_TIME_BARS[2023-09-13 05:32:58.778]: --->50-3-1-1694583170-1.074625-1.074645-1.074625-1.07464--1--1--1-
INFO: Received message: REAL_TIME_BARS[2023-09-13 05:33:01.022]: --->50-3-1-1694583175-1.07464-1.074645-1.074625-1.074625--1--1--1-
INFO: Received message: REAL_TIME_BARS[2023-09-13 05:33:06.020]: --->50-3-1-1694583180-1.074625-1.074645-1.074625-1.07464--1--1--1-
# here is a request for 5s midpoint historical bars with keep-up-to-date turned on, there are again even half a tick values
INFO: Sending message: REQUEST_HISTORICAL_DATA[2023-09-13 05:32:58.439]: ---B20-1--EUR-CASH-----IDEALPRO--USD---0--5 secs-50 S-0-MIDPOINT-2-1--
INFO: Received message: HISTORICAL_DATA[2023-09-13 05:32:58.616]: --U17-1-20230913-05:32:07-20230913-05:32:57-10-1694583120-1.074685-1.074715-1.074675-1.074715--1--1--1-1694583125-1.074715-1.074715-1.07467-1.074675--1--1--1-1694583130-1.074675-1.074675-1.074625-1.074625--1--1--1-1694583135-1.074625-1.074655-1.074625-1.074625--1--1--1-1694583140-1.074625-1.074655-1.074625-1.074645--1--1--1-1694583145-1.074645-1.07465-1.074625-1.07463--1--1--1-1694583150-1.07463-1.074645-1.07463-1.074635--1--1--1-1694583155-1.074635-1.074655-1.074635-1.074635--1--1--1-1694583160-1.074635-1.074645-1.074625-1.07464--1--1--1-1694583165-1.07464-1.074645-1.074625-1.074625--1--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:32:58.779]: ---<90-1--1-1694583170-1.074625-1.07464-1.074645-1.074625--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:33:01.023]: ---<90-1--1-1694583175-1.07464-1.074625-1.074645-1.074625--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:33:01.551]: ---=90-1--1-1694583180-1.074625-1.074625-1.074625-1.074625--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:33:06.020]: ---<90-1--1-1694583180-1.074625-1.07464-1.074645-1.074625--1--1-
# here is a request for 15m ask historical data, the values are with tick resolution (that is what it should be for bid/ask values)
INFO: Sending message: REQUEST_HISTORICAL_DATA[2023-09-13 05:32:58.440]: ---R20-2--EUR-CASH-----IDEALPRO--USD---0-20230913-05:32:58-15 mins-54000 S-0-ASK-2-0--
INFO: Received message: HISTORICAL_DATA[2023-09-13 05:32:58.656]: -- ?17-2-20230912-14:32:58-20230913-05:32:58-61-1694528100-1.07139-1.07154-1.07109-1.07135--1--1--1-1694529000-1.07135-1.07169-1.07105-1.07168--1--1--1-1694529900-1.07168-1.07178-1.07117-1.07139--1--1--1-1694530800-1.07139-1.07238-1.07138-1.07207--1--1--1-1694531700-1.07207-1.07304-1.07205-1.07299--1--1--1-1694532600-1.07299-1.07302-1.07252-1.07253--1--1--1-1694533500-1.07253-1.07286-1.07247-1.07256--1--1--1-1694534400-1.07256-1.07349-1.07256-1.07343--1--1--1-1694535300-1.07343-1.07377-1.07327-1.07328--1--1--1-1694536200-1.07328-1.07328-1.07235-1.07251--1--1--1-1694537100-1.07251-1.07258-1.07217-1.07234--1--1--1-1694538000-1.07234-1.07277-1.07233-1.07274--1--1--1-1694538900-1.07274-1.07343-1.07273-1.07326--1--1--1-1694539800-1.07326-1.07335-1.07294-1.07295--1--1--1-1694540700-1.07295-1.07337-1.07259-1.07262--1--1--1-1694541600-1.07262-1.07298-1.07247-1.07270--1--1--1-1694542500-1.07270-1.07340-1.07269-1.07335--1--1--1-1694543400-1.07335-1.07345-1.07314-1.07335--1--1--1-1694544300-1.07335-1.07340-1.07303-1.07324--1--1--1-1694545200-1.07324-1.07340-1.07311-1.07321--1--1--1-1694546100-1.07321-1.07323-1.07309-1.07310--1--1--1-1694547000-1.07310-1.07317-1.07277-1.07280--1--1--1-1694547900-1.07280-1.07301-1.07277-1.07283--1--1--1-1694548800-1.07283-1.07293-1.07278-1.07285--1--1--1-1694549700-1.07285-1.07419-1.07279-1.07414--1--1--1-1694550600-1.07414-1.07516-1.07412-1.07499--1--1--1-1694551500-1.07499-1.07652-1.07494-1.07545--1--1--1-1694553300-1.07581-1.07599-1.07537-1.07554--1--1--1-1694554200-1.07554-1.07607-1.07551-1.07602--1--1--1-1694555100-1.07602-1.07640-1.07587-1.07599--1--1--1-1694556000-1.07599-1.07611-1.07560-1.07566--1--1--1-1694556900-1.07566-1.07569-1.07548-1.07549--1--1--1-1694557800-1.07549-1.07568-1.07548-1.07559--1--1--1-1694558700-1.07559-1.07567-1.07558-1.07563--1--1--1-1694559600-1.07563-1.07572-1.07549-1.07561--1--1--1-1694560500-1.07561-1.07581-1.07561-1.07564--1--1--1-1694561400-1.07564-1.07570-1.07539-1.07549--1--1--1-1694562300-1.07549-1.07569-1.07528-1.07533--1--1--1-1694563200-1.07533-1.07643-1.07532-1.07614--1--1--1-1694564100-1.07615-1.07623-1.07570-1.07577--1--1--1-1694565000-1.07577-1.07624-1.07577-1.07614--1--1--1-1694565900-1.07614-1.07631-1.07588-1.07595--1--1--1-1694566800-1.07595-1.07618-1.07578-1.07614--1--1--1-1694567700-1.07614-1.07651-1.07597-1.07610--1--1--1-1694568600-1.07610-1.07615-1.07565-1.07566--1--1--1-1694569500-1.07566-1.07585-1.07558-1.07578--1--1--1-1694570400-1.07578-1.07601-1.07506-1.07514--1--1--1-1694571300-1.07514-1.07539-1.07483-1.07504--1--1--1-1694572200-1.07504-1.07507-1.07456-1.07464--1--1--1-1694573100-1.07464-1.07488-1.07452-1.07468--1--1--1-1694574000-1.07468-1.07490-1.07459-1.07489--1--1--1-1694574900-1.07489-1.07489-1.07445-1.07465--1--1--1-1694575800-1.07465-1.07503-1.07465-1.07479--1--1--1-1694576700-1.07479-1.07488-1.07468-1.07473--1--1--1-1694577600-1.07473-1.07480-1.07464-1.07468--1--1--1-1694578500-1.07468-1.07484-1.07463-1.07482--1--1--1-1694579400-1.07482-1.07502-1.07473-1.07501--1--1--1-1694580300-1.07501-1.07538-1.07499-1.07525--1--1--1-1694581200-1.07525-1.07548-1.07497-1.07504--1--1--1-1694582100-1.07504-1.07507-1.07462-1.07468--1--1--1-1694583000-1.07468-1.07472-1.07453-1.07465--1--1--1-
?
# here is a request for 15m bid historical data, the values are again with tick resolution
INFO: Sending message: REQUEST_HISTORICAL_DATA[2023-09-13 05:32:58.440]: ---R20-3--EUR-CASH-----IDEALPRO--USD---0-20230913-05:32:58-15 mins-54000 S-0-BID-2-0--
INFO: Received message: HISTORICAL_DATA[2023-09-13 05:32:58.726]: -- ?17-3-20230912-14:32:58-20230913-05:32:58-61-1694528100-1.07138-1.07153-1.07108-1.07134--1--1--1-1694529000-1.07134-1.07167-1.07104-1.07166--1--1--1-1694529900-1.07166-1.07176-1.07116-1.07138--1--1--1-1694530800-1.07138-1.07237-1.07137-1.07205--1--1--1-1694531700-1.07205-1.07302-1.07204-1.07298--1--1--1-1694532600-1.07298-1.07301-1.07251-1.07252--1--1--1-1694533500-1.07252-1.07284-1.07244-1.07255--1--1--1-1694534400-1.07255-1.07347-1.07255-1.07342--1--1--1-1694535300-1.07342-1.07375-1.07325-1.07325--1--1--1-1694536200-1.07325-1.07325-1.07234-1.07249--1--1--1-1694537100-1.07249-1.07255-1.07215-1.07232--1--1--1-1694538000-1.07232-1.07275-1.07232-1.07272--1--1--1-1694538900-1.07272-1.07340-1.07271-1.07322--1--1--1-1694539800-1.07322-1.07333-1.07292-1.07292--1--1--1-1694540700-1.07292-1.07335-1.07257-1.07260--1--1--1-1694541600-1.07260-1.07297-1.07245-1.07268--1--1--1-1694542500-1.07268-1.07339-1.07267-1.07334--1--1--1-1694543400-1.07334-1.07344-1.07313-1.07334--1--1--1-1694544300-1.07334-1.07338-1.07301-1.07322--1--1--1-1694545200-1.07322-1.07338-1.07310-1.07318--1--1--1-1694546100-1.07318-1.07321-1.07307-1.07309--1--1--1-1694547000-1.07309-1.07314-1.07275-1.07277--1--1--1-1694547900-1.07277-1.07300-1.07276-1.07281--1--1--1-1694548800-1.07281-1.07291-1.07276-1.07283--1--1--1-1694549700-1.07283-1.07417-1.07275-1.07413--1--1--1-1694550600-1.07413-1.07513-1.07410-1.07497--1--1--1-1694551500-1.07497-1.07649-1.07492-1.07534--1--1--1-1694553300-1.07514-1.07547-1.07514-1.07535--1--1--1-1694554200-1.07535-1.07592-1.07535-1.07588--1--1--1-1694555100-1.07588-1.07635-1.07581-1.07590--1--1--1-1694556000-1.07590-1.07607-1.07557-1.07562--1--1--1-1694556900-1.07562-1.07567-1.07544-1.07546--1--1--1-1694557800-1.07546-1.07566-1.07544-1.07556--1--1--1-1694558700-1.07556-1.07565-1.07555-1.07560--1--1--1-1694559600-1.07560-1.07569-1.07544-1.07558--1--1--1-1694560500-1.07558-1.07579-1.07558-1.07562--1--1--1-1694561400-1.07562-1.07567-1.07537-1.07546--1--1--1-1694562300-1.07546-1.07567-1.07525-1.07531--1--1--1-1694563200-1.07531-1.07642-1.07531-1.07613--1--1--1-1694564100-1.07613-1.07621-1.07568-1.07575--1--1--1-1694565000-1.07575-1.07623-1.07575-1.07612--1--1--1-1694565900-1.07612-1.07630-1.07586-1.07593--1--1--1-1694566800-1.07593-1.07616-1.07577-1.07612--1--1--1-1694567700-1.07612-1.07649-1.07596-1.07608--1--1--1-1694568600-1.07608-1.07614-1.07562-1.07564--1--1--1-1694569500-1.07564-1.07584-1.07556-1.07576--1--1--1-1694570400-1.07576-1.07599-1.07505-1.07513--1--1--1-1694571300-1.07513-1.07537-1.07483-1.07503--1--1--1-1694572200-1.07503-1.07505-1.07455-1.07463--1--1--1-1694573100-1.07463-1.07487-1.07451-1.07467--1--1--1-1694574000-1.07467-1.07489-1.07456-1.07488--1--1--1-1694574900-1.07488-1.07488-1.07444-1.07463--1--1--1-1694575800-1.07463-1.07502-1.07463-1.07477--1--1--1-1694576700-1.07477-1.07487-1.07467-1.07472--1--1--1-1694577600-1.07472-1.07478-1.07463-1.07467--1--1--1-1694578500-1.07467-1.07484-1.07462-1.07481--1--1--1-1694579400-1.07481-1.07500-1.07471-1.07499--1--1--1-1694580300-1.07499-1.07537-1.07497-1.07522--1--1--1-1694581200-1.07522-1.07546-1.07495-1.07503--1--1--1-1694582100-1.07503-1.07505-1.07461-1.07467--1--1--1-1694583000-1.07467-1.07471-1.07452-1.07463--1--1--1-
?
# here is a request for 15m bid-ask historical data, the values are again with tick resolution
INFO: Sending message: REQUEST_HISTORICAL_DATA[2023-09-13 05:32:58.440]: ---V20-4--EUR-CASH-----IDEALPRO--USD---0-20230913-05:32:58-15 mins-54000 S-0-BID_ASK-2-0--
INFO: Received message: HISTORICAL_DATA[2023-09-13 05:32:58.819]: -- ?17-4-20230912-14:32:58-20230913-05:32:58-61-1694528100-1.07129-1.07154-1.07108-1.07130--1--1--1-1694529000-1.07141-1.07169-1.07104-1.07143--1--1--1-1694529900-1.07150-1.07178-1.07116-1.07152--1--1--1-1694530800-1.07197-1.07238-1.07137-1.07199--1--1--1-1694531700-1.07260-1.07304-1.07204-1.07262--1--1--1-1694532600-1.07277-1.07302-1.07251-1.07278--1--1--1-1694533500-1.07264-1.07286-1.07244-1.07265--1--1--1-1694534400-1.07301-1.07349-1.07255-1.07303--1--1--1-1694535300-1.07349-1.07377-1.07325-1.07350--1--1--1-1694536200-1.07275-1.07328-1.07234-1.07277--1--1--1-1694537100-1.07240-1.07258-1.07215-1.07242--1--1--1-1694538000-1.07256-1.07277-1.07232-1.07258--1--1--1-1694538900-1.07306-1.07343-1.07271-1.07308--1--1--1-1694539800-1.07316-1.07335-1.07292-1.07318--1--1--1-1694540700-1.07300-1.07337-1.07257-1.07302--1--1--1-1694541600-1.07275-1.07298-1.07245-1.07277--1--1--1-1694542500-1.07296-1.07340-1.07267-1.07298--1--1--1-1694543400-1.07326-1.07345-1.07313-1.07329--1--1--1-1694544300-1.07323-1.07340-1.07301-1.07324--1--1--1-1694545200-1.07323-1.07340-1.07310-1.07325--1--1--1-1694546100-1.07312-1.07323-1.07307-1.07314--1--1--1-1694547000-1.07292-1.07317-1.07275-1.07294--1--1--1-1694547900-1.07287-1.07301-1.07276-1.07289--1--1--1-1694548800-1.07284-1.07293-1.07276-1.07286--1--1--1-1694549700-1.07344-1.07419-1.07275-1.07346--1--1--1-1694550600-1.07479-1.07516-1.07410-1.07481--1--1--1-1694551500-1.07578-1.07652-1.07492-1.07582--1--1--1-1694553300-1.07537-1.07599-1.07514-1.07562--1--1--1-1694554200-1.07556-1.07607-1.07535-1.07570--1--1--1-1694555100-1.07603-1.07640-1.07581-1.07609--1--1--1-1694556000-1.07574-1.07611-1.07557-1.07579--1--1--1-1694556900-1.07555-1.07569-1.07544-1.07558--1--1--1-1694557800-1.07554-1.07568-1.07544-1.07557--1--1--1-1694558700-1.07558-1.07567-1.07555-1.07560--1--1--1-1694559600-1.07559-1.07572-1.07544-1.07562--1--1--1-1694560500-1.07569-1.07581-1.07558-1.07571--1--1--1-1694561400-1.07552-1.07570-1.07537-1.07555--1--1--1-1694562300-1.07549-1.07569-1.07525-1.07551--1--1--1-1694563200-1.07603-1.07643-1.07531-1.07605--1--1--1-1694564100-1.07593-1.07623-1.07568-1.07595--1--1--1-1694565000-1.07609-1.07624-1.07575-1.07610--1--1--1-1694565900-1.07609-1.07631-1.07586-1.07611--1--1--1-1694566800-1.07597-1.07618-1.07577-1.07598--1--1--1-1694567700-1.07623-1.07651-1.07596-1.07625--1--1--1-1694568600-1.07588-1.07615-1.07562-1.07590--1--1--1-1694569500-1.07570-1.07585-1.07556-1.07572--1--1--1-1694570400-1.07557-1.07601-1.07505-1.07558--1--1--1-1694571300-1.07513-1.07539-1.07483-1.07514--1--1--1-1694572200-1.07482-1.07507-1.07455-1.07484--1--1--1-1694573100-1.07470-1.07488-1.07451-1.07471--1--1--1-1694574000-1.07474-1.07490-1.07456-1.07476--1--1--1-1694574900-1.07468-1.07489-1.07444-1.07470--1--1--1-1694575800-1.07483-1.07503-1.07463-1.07484--1--1--1-1694576700-1.07478-1.07488-1.07467-1.07479--1--1--1-1694577600-1.07472-1.07480-1.07463-1.07473--1--1--1-1694578500-1.07472-1.07484-1.07462-1.07474--1--1--1-1694579400-1.07485-1.07502-1.07471-1.07487--1--1--1-1694580300-1.07519-1.07538-1.07497-1.07520--1--1--1-1694581200-1.07525-1.07548-1.07495-1.07527--1--1--1-1694582100-1.07477-1.07507-1.07461-1.07479--1--1--1-1694583000-1.07463-1.07472-1.07452-1.07464--1--1--1-
?
# here is a request for 15m midpoint historical data with keep-up-to-date turned on, the values are with half a tick resolution, both the historical and the real-time
INFO: Sending message: REQUEST_HISTORICAL_DATA[2023-09-13 05:32:58.441]: ---F20-5--EUR-CASH-----IDEALPRO--USD---0--15 mins-54000 S-0-MIDPOINT-2-1--
INFO: Received message: HISTORICAL_DATA[2023-09-13 05:32:58.890]: --
17-5-20230912-14:32:57-20230913-05:32:57-61-1694528100-1.071385-1.071535-1.071085-1.071345--1--1--1-1694529000-1.071345-1.07168-1.071045-1.07167--1--1--1-1694529900-1.07167-1.07177-1.071165-1.071385--1--1--1-1694530800-1.071385-1.072375-1.071375-1.07206--1--1--1-1694531700-1.07206-1.07303-1.072045-1.072985--1--1--1-1694532600-1.072985-1.073015-1.072515-1.072525--1--1--1-1694533500-1.072525-1.07285-1.072455-1.072555--1--1--1-1694534400-1.072555-1.07348-1.072555-1.073425--1--1--1-1694535300-1.073425-1.07376-1.07326-1.073265--1--1--1-1694536200-1.073265-1.073265-1.072345-1.07250--1--1--1-1694537100-1.07250-1.072565-1.07216-1.07233--1--1--1-1694538000-1.07233-1.07276-1.072325-1.07273--1--1--1-1694538900-1.07273-1.073415-1.07272-1.07324--1--1--1-1694539800-1.07324-1.07334-1.07293-1.072935--1--1--1-1694540700-1.072935-1.07336-1.07258-1.07261--1--1--1-1694541600-1.07261-1.072975-1.07246-1.07269--1--1--1-1694542500-1.07269-1.073395-1.07268-1.073345--1--1--1-1694543400-1.073345-1.073445-1.073135-1.073345--1--1--1-1694544300-1.073345-1.07339-1.07302-1.07323--1--1--1-1694545200-1.07323-1.07339-1.073105-1.073195--1--1--1-1694546100-1.073195-1.07322-1.07308-1.073095--1--1--1-1694547000-1.073095-1.073155-1.07276-1.072785--1--1--1-1694547900-1.072785-1.073005-1.072765-1.07282--1--1--1-1694548800-1.07282-1.07292-1.07277-1.07284--1--1--1-1694549700-1.07284-1.07418-1.07277-1.074135--1--1--1-1694550600-1.074135-1.075145-1.07411-1.07498--1--1--1-1694551500-1.07498-1.076505-1.07493-1.075395--1--1--1-1694553300-1.075475-1.075665-1.075315-1.075445--1--1--1-1694554200-1.075445-1.075985-1.07543-1.07595--1--1--1-1694555100-1.07595-1.076375-1.075845-1.075945--1--1--1-1694556000-1.075945-1.07609-1.075595-1.07564--1--1--1-1694556900-1.07564-1.07568-1.07546-1.075475--1--1--1-1694557800-1.075475-1.07567-1.07546-1.075575--1--1--1-1694558700-1.075575-1.07566-1.075565-1.075615--1--1--1-1694559600-1.075615-1.075705-1.075465-1.075595--1--1--1-1694560500-1.075595-1.07580-1.075595-1.07563--1--1--1-1694561400-1.07563-1.075685-1.075375-1.075475--1--1--1-1694562300-1.075475-1.07568-1.075265-1.07532--1--1--1-1694563200-1.07532-1.07642-1.075315-1.07614--1--1--1-1694564100-1.07614-1.076225-1.07569-1.07576--1--1--1-1694565000-1.07576-1.076235-1.07576-1.07613--1--1--1-1694565900-1.07613-1.07631-1.075875-1.07594--1--1--1-1694566800-1.07594-1.07617-1.075775-1.07613--1--1--1-1694567700-1.07613-1.07650-1.07597-1.07609--1--1--1-1694568600-1.07609-1.076145-1.075635-1.07565--1--1--1-1694569500-1.07565-1.075845-1.07557-1.07577--1--1--1-1694570400-1.07577-1.07600-1.075055-1.075135--1--1--1-1694571300-1.075135-1.075375-1.074835-1.075035--1--1--1-1694572200-1.075035-1.07506-1.074555-1.074635--1--1--1-1694573100-1.074635-1.074875-1.074515-1.074675--1--1--1-1694574000-1.074675-1.074895-1.074575-1.074885--1--1--1-1694574900-1.074885-1.074885-1.074445-1.07464--1--1--1-1694575800-1.07464-1.075025-1.07464-1.07478--1--1--1-1694576700-1.07478-1.074875-1.07467-1.074725--1--1--1-1694577600-1.074725-1.07479-1.074635-1.074675--1--1--1-1694578500-1.074675-1.074835-1.074625-1.074815--1--1--1-1694579400-1.074815-1.07501-1.07472-1.07500--1--1--1-1694580300-1.07500-1.075375-1.07498-1.075235--1--1--1-1694581200-1.075235-1.07547-1.07496-1.075035--1--1--1-1694582100-1.075035-1.07506-1.074615-1.074675--1--1--1-1694583000-1.074675-1.074715-1.074525-1.074625--1--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:33:01.023]: ---=90-5--1-1694583000-1.074675-1.074625-1.074715-1.074525--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:33:01.551]: ---=90-5--1-1694583000-1.074675-1.074625-1.074715-1.074525--1--1-
INFO: Received message: HISTORICAL_DATA_UPDATE[2023-09-13 05:33:06.021]: ---<90-5--1-1694583000-1.074675-1.07464-1.074715-1.074525--1--1-
i'm running ib gateway 10.25.1f, it worked also yesterday with 10.25.1e.
