This is particularly problematic when removing lots of duplicates, but have tested and the behaviour happens with a single paper as well.
Example steps to reproduce:
- Create a shared folder
- Move a paper from my own library to the shared folder
- Create a duplicate of that paper (e.g. via the import paper button)
- Merge that duplicated pair of papers
- Notice that the paper in the shared folder now appears twice
(I don’t think this adds much, but I’ve noticed that this doesn’t affect papers that were added by collaborators to the shared folders)