This probably got reported somewhere before, but I couldn’t find a report so I thought it’s worth a shot to bring this up.
If you have a multi-monitor setup and a NUI has focus the mouse can move off the screen.
For example: You have FiveM focused on your main screen and have a second screen on the right. If you move your mouse to the right border of your game window it doesn’t stop there but actually moves to the second screen.
This also happens if the mouse has no focus, making this really ‘annoying’ when moving your cam around (For reference, using: SetNuiFocus(true, false)).
Probably related bug:
If you have a multi-monitor setup and join a server the mouse also moves off the screen, even when no NUI has focus (normal gameview). You need to minimize and then refocus FiveM to stop this behavior from appearing.
This behavior is consistent on all screen type settings (exclusive, fullscreen, windowed) and mouse input settings.
I cannot remember when this issue started to occur (maybe existing since CEF got added?).