Sounds like some sort of overlay is trying to display, not showing up and restricting mouse movement. Are you running other software alongside the game? I.e. Twitch, Discord, etc. Also worth checking graphics driver/software and any lightning/mouse/keyboard software for any overlays as well. Also, check Windows settings for Sticky Keys - I believe the shortcut for those is the Shift key pressed something like 5 times in a short space - you could be activating this.