If you enter two labels with different names but the same catalog number, the release editor will suggest the label/catno pair already exists until you search and select at least one of them (it's probably comparing on label ID, which is missing for both since they are unselected?).

This is of course super confusing for any user who looks at this and thinks "wait, one is label a and the other is label b, what is going on".

We should probably check if the name differs if both pairs have no ID.