Right thats what i was thinking too. I've tried every thing i can think of from multiple screens to get the mouse to lock into the game its self too updating drivers too looking for a settings.JSON file to try and add or edit the mouse inputs.
I would say it was just the game however it has happened to me on multiple games not just one, for instance baby in yellow for example and hungry lamu do the same thing and im pretty sure those games have mouse look controls.
I'm thinking maybe its a ram issue because I'm sitting at a 83% on ram usage so that might be causing the problem however if i open a game from steam that i know has mouse look inputs it works fine.
For instance i was playing myst last night after i made this post and the mouse worked fine. I'm beginning to think its something with my ram being low or its a issue with itch games not fully loading with the unity engine perhaps?
I'm at a loss atm tbh spent all day yesterday trying to figure it out, I think today I'm going to clean as much ram up as physically possible and see if that helps any.