I wonder if it bombs because you're trying to attach the same PNR to two different profiles?

Or maybe it edit checks the FF number you have on the reservation against the FF number on the profile?

In the past (and this is the MM world of course) if Brian and I were booked on the same PNR, and both our FF numbers were on the individual reservations, I could attach that single PNR to both his profile and to mine. But if they were booked as separate PNR's, I couldn't attach his to mine (for example) because the FF number (his) didn't match the FF number on the profile (mine). Maybe that kind of issue will prevent you from having that one PNR attached to both your ex-MM profile and your new-ER profile?