I didn’t think I was blindly changing this. The tags were slightly different, and I merged them. I’d be happy to hear what I did wrong. As far as I can tell, only the self relationship was lost and the rest of the data was kept. I thought that the relationship was supposed to work with other parts of the building and not the bottom part relating to itself on the lower part. Perhaps the relationship of the bottom part was supposed to be for the top part instead?