I found a rather annoying bug tied to the controls. Particularly the mouse.
What happened is that randomly, the mouse will suddenly move at one point to the next in a single frame (making it look instantaneous.
Strangely, the bug seems to react differently depending on which mode I'm in. In "Look" mode (the one with crosshairs), it causes my character to randomly do a 90? turn (either left or right). In "Cursor" mode (where the mouse only moves a cursor), it seems to go randomly to one of the corners of the screen (either of them, but the bottom ones are the most frequent).
I also need to add that the bug only happens while the mouse is moving (and in some cases, when I'm moving).
I previously thought that having a controller plugged in caused the bug, but I played again tonight (and finished the first quest) and the bug was still present (and rather frequent).
If there's any more information you need (conputer specs, OS, mouse used, Dxdiag file), just ask.
Thanks in advance.