For jittery mouse movement or the mouse not working well, GOG has the following suggestion for Overseer:
Disable Mouse Acceleration
Try disabling the Enhance pointer precision option. To do this, please follow these steps:
Windows 10:
Press WinKey+R, and in the Run window type:
control
After that press Ok, and navigate to Mouse -> Pointer Options, then make sure that Enhance pointer precision is unchecked, and click OK.
I don't know if this will work for your problem or maybe you have already tried this, but it's worth a shot and you can always change it back to the way it was before.