Oh thank you very much!! I did not realize that this could be a problem.
I just saw this post again and realised that I did not yet say how I solved it in the end. Copying the levels was indeed also a solution, however the client did not want extra levels in his model. Which I could understand. So I copied the elements from the linked model to the current model and in order to move them to the correct location i had to copy them again, set the location of the new element and delete the old.