Mouse issues with "We Were Here" and "We Were Here Too"

I've looked through all the discussions on steam about mouse issues but this seems to be something different. I did, however, disable steam input for controllers for the games, and that didn't seem to help.

Ok, the issue: When I look vaguely towards a interactable object, the mouse speed slows to a crawl, and afterwards is really unpredictable, sometimes increasing to maybe 5x normal sensitivity, sometimes continuing to be slow. I had to look away from things and strafe because I couldn't reliably change the direction. I was Librarian in the first game so I could work around it (and I was bringing a new person to run through the games so I put up with it), but that won't fly for the second game.

Has anyone heard of anything like that happen?