AGO has a prospective deal on the table from Flagstar or Credit Suisse or another and Moody's is holding off, waiting to see if AGO takes the offer. It may make the difference and gives Moody's cover to re-affirm AA-
My guess is that Moody's models are so off the mark that AGO management keeps them going back to correct them. Moody's wants to downgrade but then it would be against the criteria itself.