I didn’t really know how to word the title, but the MouseBehavior property of the UserInputService behaves differently on client than it does in studio, at least when the camera is set to Custom. In studio, setting this to anything other than Default causes the camera to not be able to move, while on the client, the camera moves as if you were panning.
I’m not really sure which one has the right behavior, so I guessed and went with studio.
A simple 2 line reproduction can be found here.
It’s uncopylocked so you can see how it works in studio.