I think I would do a search in the schema for ldapDisplayName=DUP-loginShell-591f5fe1-f2eb-4402-9e09-058409f8387 and see what you can find. It looks like something weird has happened to the schema. I've never seen this problem before. I also don't know what that attribute is (never seen it or used it). I think you can change the name if you need to.
It may also be the case that there is another attribute with the name loginShell that is in the schema but not associated with your object here and thus some cleanup may be required.
You may be best served getting someone from MS support to help out here if you can't figure out the schema problem at the client.