Are both UPN types in the same BaseDN search path?
If not, are all domain controllers servicing those realms ... sometimes I have seen a fraction of the Domain Controllers serve as KDCs for a given realm.
Did you add all realms as required for this?
Unfortunately, there are lots of variables to try and sort this out. I wonder if you might be better with a Support Request for someone to review this with you. (webex and direct back and forth)