Merge can create duplicate Tracks
When you merge 2 albums which have the same tracks (same name), the tracks themselves don't get merged, so after the merge you have the same track twice which breaks the listenbrainz worker (when looking for a track it uses get_by which expects ONE result only)
After merging "Compositions for Piano" by The flashbulb, there are now 2 tracks with the name "Morning Run"
Deleting a branch is permanent. It CANNOT be undone. Continue?