When you hold down the secondary mouse button on your mouse, the mouse will have its position in the game window locked until you release the button. This happens regardless of whether you set MouseBehavior. The CameraScript I have included in this repro in StarterPlayerScripts is your default “Hello world!”.
That’s probably due to the default camera scripts.
Try overwriting them with an empty script and then see if it happens.
Please read the thread before responding. This is a genuine bug.
Thanks for bringing this up. We’ve figure out what the issue is and will get a fix out likely in next weeks release.
Still having issues, did the fix go out?