Camera.main doesn't exist for anyone who isn't MasterClient

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This is an error that's kind of appeared out of nowhere. Any reference at all to the camera results in an error. I haven't touched the camera at all for quite a long time, but all of a sudden it stopped working for non MasterClients.

Trying to use the camera or anything attached to the camera at all returns either an "Object reference not set to an instance of an object" error or "The objective of type 'Transform' has been destroyed but you are still trying to access it".

There's no Photon View or anything related to Photon working with the camera, it's already in the scene when the game starts. When I play as a client through the editor I can very clearly see that the camera is there (and set to main camera), but no scripts are able to find it.