Had a weird bug where, after alt+Tabbing out, it limited my turn movement to exactly 450 degrees (as in I could only turn around 1 1/4 times and then hit an invisible wall).
EDIT: It appears to be consistently replicable by talking to any NPC. I think it must be unlocking my mouse from the game screen every time I click a dialogue option. Clicking anywhere in the screen brings it back into focus and solves the issue.
Steps to replicate:
Talk to ANY NPC
Click Leave
Attempt to turn in any direction without clicking again