So when playing this game at first the mouse felt fine and it controlled well. Now for some reason I can't look around without flinging my mouse really fast and even then it is uncontrollable because the mouse is being flung. I can't move the mouse slowly because it doesn't seem to recognize that the mouse is even moving. It seemingly only recognizes that the mouse is moving when I move it at an extreme speed. The mouse feels very restricted to a X and Y axis and I can't move it vertically as well unless again I really force it. Even when I set the mouse sensitivity high in game it still won't look unless I'm moving my mouse insanely fast. I know it isn't my mouse DPI because it's at 1520. When I turn down my mouse DPI I can't even look around at all it just locks up because the mouse isn't moving fast enough for it to register. The mouse also works fine in the main menu so I have no clue whats going on. I have seen gameplay and it didn't seem to be how this game actually is supposed to be. I can't find anything about this so I hope someone knows what I'm talking about and has had this problem before. Thank you!

Well I figured out how to fix the jittery mouse look. I just had to disable the “enhance pointer precision” option. To do this, go to Start -> Control Panel -> Mouse -> Pointer Options, then make sure that “Enhance pointer precision” is un-checked, and click OK. The whole time this was on the GOG support.