How to restrict instantiation of objects to one particular scene?

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Hiiii.
I have got a weird behaviour in my game.

At first a client open a game and it loads a Menu scene, then the client creates a room and loads a new scene. In this new scene I create a few NPC characters using PhotonNetwork.InstantiateSceneObject method.
Then another one client opens the game and see the Menu scene, then he searches for a room, and when find one, connects to this room. After this he gets signal from the MasterClient to instantiate an NPC, but the client is still in Menu scene. So at first the NPCs are created in the Menu scene, and after this the client loads a new scene, and of course, this scene has no NPCs.

How to instantiate NPCs only in the second scene, and not in the Menu scene?

MasterClient activity
Client activity