Hi Peter,
An interesting thing I noticed with the aircraft looping bug. Sitting in the back seat of a student's Typhoon, I asked him for a slow loop ( 3G ) at 400KIAS. As the aircraft went over the loop, there were subtle twitches in both verticals, and the usual momentary "out of control" moment as we reached the inverted. JoinFS recovered by the point where the Typhoon was just past the vertical dive out of the loop.
What's interesting was that when I asked the student for a high-G loop ( 5-6G, 400KIAS ) the bug vanished. It seems that the longer one remains in a vertical manoeuvre, the more likely the bug is to surface.
Hope this helps,
Cheers,