GreenSwede
GreenSwede
Found one more area where it happens. 
If this was to be implemented officially, a cvar toggling the functionality would be the best approach in my opinion.
This is still an issue with version 3.16.4 when attempting to play Team Fortress 2. Mouse goes upside down and hits the window boundaries when aiming, there are no issues...
Check your temperatures while running the game. You may want to stresstest your PC with a benchmark tool to see if you can replicate the reboot, e.g. "Geeks3D FurMark" as...