This probably means that you have created a new rem instead of linking to it in some moment. This happens to me and apparently to some other users (if you hit ctrl+enter when trying to make a reference, it creates a new rem, but it also happens if you have your mouse there for some reason). The solution is twofold:
For already duplicated rems, go to the new one (most likely the one you have without parents) and merge it with the old one ( ctrl+alt+shift+E
and select the old one).
In the future, try to make sure you don’t create new rems instead of referencing existing ones, by paying attention to where your mouse is, basically.
Let me know if this works