I have this problem as a new player. Thanks for looking into it.
For me it seems to be related to UI boxes, such as the invisible box around a corpse on the ground. The cursor can get stuck inside the box, but if I move the view with the keyboard while the bug is in effect, it can also get stuck
outside, meaning the cursor moves around fine while it's outside the box but seems to be repelled by the invisible edge of the box (presumably the cursor is center-locked only while within the box).
- Entering and leaving mouse look mode always fixes it (though sometimes you have to move the view with the keyboard to do this).
- It happens in both windowed and full screen mode.
- Enabling NoSlowBoxes had no effect.
- The window causing the problem doesn't seem to need to be covering the screen center.
It happens for me maybe 50% of the time I kill an enemy.