Problem with loading level

The project has two scenes: login scene and combat scene. First load login scene, then combat scene. If a player is idle for a long time, it throws in a scene login. In the Unity it works perfectly, but in any player (web or standalone) shows two scenes at the same time. What’s the problem?

If you haven’t got a camera, it’ll generally just show junk (What is in the screen buffer at that time) in built clients - the editor clears the screen buffer so generally masks the problem.

I would add in a camera with a solid color which suits your game as the clear color, which should fix the issue