Weird output message I receive sometimes when I go into Solo Mode...?

So you know when you do the Start Server thing, and you choose the amount of players you want and press "Start"?

I do that, and I always get 1-4 windows/players that get this:

StarterGui:GetCoreGuiEnabled called from server script. Did you mean to use a local script?

The windows that get this, the camera is stuck and focused at 0,0,0 instead of the Player. How can I fix this?

NOTE: The output message is shown in yellow.