At least in some cases, a patron whose authorization_identifier changes will stop having their circulation manager account synced with their ILS account. This is supposed to happen every twelve hours, and it's supposed to happen even if your authorization_identifier changes.

If the patron tries to authenticate with their authorization_identifier, they won't be able to log in. If they authenticate with their username, everything will apparently work, but their account isn't being synced anymore.

It's not clear to me under what circumstances this happens, but once it's fixed things should start getting better automatically.