You could try disable fullscreen optimisations it usually fixes mouse stutter.
Navigate to your game files and locate the r5apex.exe
then right click and open properties then click the compatability tab
tick the disable fullscreen optimisations and apply.
run the game to test.
Already had that option enabled since the game came out to minimize crashes, issue comes from the game itself. Like i said, didn't change any video settings at all. Hardware & Drivers are the same as a week ago. Probably there's some Engine bug because of that "FPS Cap up to 300" they mentioned on patch notes causing micro-stutters and mice stop responding because of it.
