I had the Problem several times while flying to Frankfurt (EDDF).
It seems, that the FMS is calculating every 5 seconds a new route…
The problem occurs on other routes too.
While changing the sim rate to 4x all inputs to the aircraft were frozen completely after few minutes of flying. Neither i was able to deactivate the sim rate.
During the final approach, I deactivated the autopilot. The alarm started ringing. Instead of going off by itself after a few seconds, the alarm kept ringing until after landing. Even the master caution button did not help to deactivate the alarm.