Hello Sascha,
Great detective work in pinpointing the problem.
Your mod should work as in non-AM mode you revert to the standard CW timeout logic.
It is easy to verify but trying to send in CW.?
The timeout you are seeing is the one set as the CW delay to return to Rx which can be changed in the menu.
If the key has not been pressed for that delay value, the rig returns to Rx, and since we are never closing the key (Arduino input A6) in that AM mode it simply returned to Rx automatically.
Thanks for keeping us informed.
73, John
