In my Pimax Crystal (RTX 5090) I experience a drop in FPS with stutters about 20 or so minutes into a flight, if I go temporarily go back into 2D and then back into VR the FPS recovers. Any thoughts?

I see the same thing with a Quest 3 on a 4090.  If I fly a helicopter low over a forest, the frame rate drops.  This is perhaps not surprising, but it does not recover when I move on.  Hitting the escape key twice (out of, then back into VR) restores it quickly.  Actually, you are still in VR, but in 2D mode.

Edited February 27Feb 27 by Grindathotte