Steps to reproduce:

1. Edit an existing release
2. Open the tracklist tab
3. (This seems to be key to reproducing) Open the AC bubble by clicking on "Edit" next to a track artist
4. Select a different artist by searching or by pasting a MBID
5. The existing AC will be retained in some cases and wiped in others, without any apparent consistency.

It would be good if this could be made consistent. Perhaps, if /not/ opening the AC bubble consistently wipes the existing AC, editing with the AC bubble open should allow editors to retain it, but this is not a strong preference.