MultiplayerSpawner not working when instantiated on client after the host

[ghost]

Godot version

v4.0.alpha10.official [4bbe7f0]

System information

Windows 10

Issue description

I've been getting some very buggy behavior with the MultiplayerSpawner when instantiating it

If you're connected to a server as a client, and instantiate a scene containing a MultiplayerSpawner AFTER the host has already instantiated that same scene & the host has already instantiated scenes for the MultiplayerSpawner to spawn, the MultiplayerSpawner just won't work on the client

The following error will be spit out by the client:

Steps to reproduce

Simply load a scene containing a MultiplayerSpawner as a client after the host has already loaded that same scene & has instantiated scenes for the MultiplayerSpawner to spawn

Minimal reproduction project

MultiplayerSpawner bug.zip

[jgillich]

I've also come across this in #62027. What is odd is that the multiplayer_bomber example works fine, and I believe it creates the server scene first. So it seems this problem only occurs when you join a bit later than the server