All objects have moved out on coordinate Z

Can’t change Z of what, the camera? Or something else? A script could be doing it.

That’s an interesting question. Perhaps by adding an EventTrigger class to the button you can control more precisely what you respond to?? I haven’t tested it but that’s the first thing that comes to mind.

As for copying stuff around, that’s always a bad way to work.

Additive scene loading is one possible solution:

A multi-scene loader thingy:

My typical Scene Loader:

Other notes on additive scene loading:

Timing of scene loading:

Also, if something exists only in one scene, DO NOT MAKE A PREFAB out of it. It’s a waste of time and needlessly splits your work between two files, the prefab and the scene, leading to many possible errors and edge cases.

Two similar examples of checking if everything is ready to go: