I am developing games on unity, but i have bad experiences of lags and things like this. I think it might be some problems with material of this picture. This happens in unity, when material have different render pipe line. For example, in mostly all games BRP(Basic Render Pipeline) is used, in some games either URP(Universal Render Pipeline) or HDRP(The High Definition Render Pipeline). When you use materials from different RP(Render Pipeline), your material and textures can become some sort of glow-purple, like in this screenshot. I do not know personally how to fix this problem, but you can try to find the material with texture of this background in earlier version, and put it instead of the broken one. If problem is not in this, i am sorry. This is the only thing i can think about.