The barcode input window has stopped working. When you enter the correct code, everything is fine. But when you enter the real code from the back cover, you click "I confirm that this is the barcode as it appears on the release", then you enter the tracklist, etc. to the end, then the error goes out!
Try to enter the barcode in the annotation of https://musicbrainz.org/release/69ce5dc9-e1e1-41c2-b993-431e12e1e48d