I believe this is a bug that occurs in TWS 10.30+
I see this message when trying to modify the limit or stop price of an OCA order in TWS 10.30+; same code works fine in TWS 10.19.
TWS log shows that there is no OCA group revision.
There is also a related error ("OCA handling method mismatch") which (I think) occurs when submitting dependent OCA orders (again, only TWS 10.30+)
OCA orders are really messed up in 10.30+, and I have an IB ticket that TWS API support is investigating (ticket #804191, if you would like to contribute).
