I had my rover basically tuned and working just a few weeks ago.
But now suddenly doing stupid things like starting with last MP first and not following waypoints.
GPS appears to be working fine and compass shows correct direction in my ground-station.
Thanks
Update: From my own diagnostics it would appear that a difference in compass readings is the issue. This would make sense as many others reported problems with unreliable compass due to interference caused by various elements on a a large rover, like a ride on mower for example.
I guess from here the best solution would be using 2 GPS receivers for yaw control, rather than compass.
Hope this somewhat helpful for others with such problems.