Hi @dienat , when you first got the issue about the objects getting pink, did you see the “Maximum number (256) of shader global keywords exceeded” error in the player log? If you use a lot of third party packages, you could easily hit this limit, take a look here to understand better why it happens and what we are working on to improve this situation.
About the other error, the Unity’s serialized files do have a limit for the maximum file size. The file contains a header and one of the fields inside the header is size, this is stored as a 32 bit unsigned integer, the limit of which is 4GB. The development team has been working on a solution for this for long time to support a 64bit unsigned integer and allow bigger serialized files. Fortunately, Unity 2020.1 brings some changes to file access to support files larger than 4GB on 64 bits platforms. Take a look at this [post]( Bug: 4GB limit to Textures in standalone build page-5#post-5300130).
I’m still not sure why moving everything to a different scene solved the shader keywords issue as you are still using the same assets but on other scene.
About how to solve the 4GB file size limit, the assetbundles is the more direct solution, however, addresables assets is another option you could try, this way you can also avoid the issue.