I've been getting the same issue. Just have to press any mouse button and the camera will turn back to the direction it last was when the menu was open.
Game hasn't crashed but the mouse issue is annoying. Did try a different mouse. Same issue.
Not sure if it's a wayland issue or not.
The Windows client does not have this issue.
Update: Ok turns out it is a Wayland issue. Switching back to X11 resolves the mouse position snapping issue.
Artix Linux
Kernel 5.8.12
Mono 6.10.0
Mesa 20.3-git
LLVM 12.0
Vintage Story 1.13.4
