FlightFX P180 Autopilot problems

Before asking if anyone has experienced this issue, let me state the following:

I am on PC. I undestand flight planning and have flown a bunch of FS2020 aircraft with FMC’s using RNav and ILS approaches successfully.

I have also done this with the FlightFXP180, which is a great aircrast to fly, without problems. However, this is the second time this has happened. I’m on a flight, getting pretty close to the programmed approach. All of a sudden the autopilot makes a weird sound, goes off, and the plane starts rolling. I recover and turn on Autopilot again. I can go into heading mode and I can use VS or FLC. But I cannot go into NAV, either with my assigned hardware button or by pressing it with the mouse on the aircraft panel. NAV will not work no matter what. Since this does not happen on every flight it cannot be something I’m doing wrong biut I assume it is a bug (?)

The only recourse is to do a manual approach which is not always fun on a very cloudy day.

Has anyone else had this happen?