I have also encountered this issue, extreme non-sensical wing flexing particularly during pushback, engine start and taxiing. FPS drops also occurred during this time. Another issue is when changing from cockpit view to external view, the tail if the aircraft is missing for a few seconds then loads. Switching from inside to outside view also dramatically lowers FPS to the point that I can only taxi using cockpit view as changing to the external view would cause freezes and stutters.