The problem is your uv maps, Christoffer. They’re simply not good. Did you ask unreal engine to generate them for you when you imported your meshes or you’ve done them yourself in your 3d modeling software?
-Best solution is to make them yourself (unwrap channel 2 in 3ds with a plugin like steamroller, it’s the easiest and fastest way)
-If you prefer you can let unreal auto-generate on import them but don’t expect nice results, it’s not really working well imo.
-If you have a mesh with a couple objects with a uv channel on each objects (in ), don’t ‘‘combine meshes’’ when importing in unreal engine, it will merge all 2nd uv channels together and you’ll get the errors you are getting!
Good luck!