"I looks like I meanwhile found the cause of the problem. The manufacturer of motor did a mistake in its datasheet. Recommended 13x5.5 prop with 4S is probably wrong. The motor can't handle this prop on 4S. It should be either smaller prop or 3S…"
thanks for your answer. I got the file, uploaded to ESC, but unfortunately it didn't help. Sync loss problem is still there. :-/ For reference, here is the issue thread I have posted on github: https://github.com/sim-/tgy/issues/50"