http://musicbrainz.org/edit/16021914

Modbot said "This relationship has already been deleted" even though the relationship still exists.

First, the relationship still exists (http://musicbrainz.org/recording/20299ecf-3780-4690-855c-53149cb68cd0)

Second, even if it had been deleted, "already" implies that this edit is a remove edit, which it isn't. It should just say "This relationship has been deleted" (but of course only if it actually has, which is not the case here)

What appears to have happened here is that other recordings were merged into this one, and the merge kept the wrong relationship (one of the ones on a source recording, instead of the one on the destination recording). So modbot thought it was deleted, and failed the edit incorrectly.