I have had similar issues with it. The route mode doesn't seem to head to the waypoints even after choosing the waypoint on PVI and setting route mode. Sometimes it just seems to turn in a lazy circle. Other times it seems to be following a diamond pip on the HUD compass tape that doesn't seem to align to any of the waypoints at all.
Also, not sure how the ARBIS (?) fits in with the PVI -as the "to" waypoint on there doesn't seem to coincide with the PVI set one - but it does update when passing the waypoint (which I've had to fly to manually to trigger). The way the map moves in that thing is fucking frustrating too!