Why does this happen and how do I fix it
Not aware of the UVs getting changed, but the problem is epic.
A year or so ago they forced a new import system onto the engine that hasn’t worked right ever (because like the rest of the engine it’s made and managed by people who need to work at Mc Donald’s ^^)
Simply remove that/disable it and go back to the importer that actually works. Usually that fixes any issue.
So long as the issue isn’t you.
When you import a mesh unless you tell it not to, the engine will generate a light uv map. Maybe you are generating one and just using that instead of your proper UV.
nevermind I fixed it! the uvs had another channel for some reason on blender

