Moving on the ground and looking around, or anything that makes the camera to move (bumps etc) quickly erodes frames and then they settle at exactly 10fps and 100ms on the FPS display.
These frames remain low until I exit or reload/change the aircraft. When I do that, frames instantly go back to 40-50. If I’m then in the air, there’s no slowdown no matter what I do, until I touch the ground again.