I think this issue was caused by Marriott's system allows about 1 year ahead of time booking, while old SPG systems allows way longer than that. The M&A IT didn't take this into consideration, so the system won't be able to handle the refund of the "old" SPG reservations which were booked way ahead of time. I personally got about 200K+ points stuck in the misery, due to a cancellation at right after the merger on a X'Mas booking (this year) which was maded in August last year.