RenderTexture does not show up right, after saving?

I gave my camera a renderTexture as Target Texture so I could put that renderTexture into a rawimage on my canvas and get this pixelated effect. (Picture 1) But whenever I save the scene or the full project and reopen it, it looks like this again or I cant move at all. Same happens, when I build my project. (Picture 2)

If I redo the renderTexture it fixes that temporarily but I want a solution so I can also build my project.

How can I fix this? Version: 5.5.0f3