Question Editor / Playmode works fine. Reference Errors in Build Mode

Hello Guys,

so I wanted to test out my game and built it for Windows 64 bit. When I launch my game there are Null Reference Errors which doesn't appear in play mode /editor. Because of that, it's impossible something is not set up right because in play mode everything works fine.

The problem seems to occure when I try to find a GameObject with "Find" as well as "FindObjectOfType". It seems like the built game is not able to find GameObjects in the scene. How is this possible and what can I do?

I know "Find" is always not to good for performance and maybe you say: Just find the scripts on another way. But this seems like a big problem right?

There are no other errors shown in the console.