Unfortunately I am not aware of Case Closed being deemed good enough for CEDR. But it would be interesting to try it out, just in case the advent of AI has changed things. Just use that as a screen shot, put in a CEDR submission. After a few days you will get a message querying whether BA has issued deadlock, send them that screenshot and any evidence that you tried to get BA to re-open. That part of CEDR is relatively simple, and the worst they can say is "wait x more weeks", it won't damage your claim.