Exporting a scene as a package and importing it in a new project causes graphical issues. Why?

Questions & Answers
1

Lighmapping gets a bit weird and on top of that some textures gets some weird seams. This happens when i export the scene as a package and import that package in a new project.

We are developing an art asset and we just need to know how to make the package work like it should.

2

Finally, the issue is in the occlusion. But i don’t understand why it looks bad when i “reimport” in another project. Neither do i understand how to fix it.