1. Open a relationship editor session
2. Add a relationship to a recording (from the release) from outside the relationship editor
3. Try to add the same relationship from the previously opened relationship editor session (which doesn't yet know it's already there)

Expected result: it either ignores that rel and submits, or says why it has failed to submit.
Actual result: the whole thing fails to submit, but just makes the Enter Edit button green again without any hint of what has happened at all.