Had a similar (but possibly related) problem landing in the north western area of the Rhinewin terrain once, when in a P-47.
I kept smashing into invisible things, and wound up pointed upwards on an invisible slope, without any trees for hundreds of feet around and on what appeared to be an entirely flat plane. I'll try and dig out the video/screenshots soon, and post them here.
This was in the Patch 2, offline.
<S>
Yossarian