I had opened a case through our AppleCare Alliance contract and was told that (1) MS and Apple were aware of the issue and (2) that this was Microsoft's issue to fix. It apparently has something to do with security changes related to how apps manage memory and that the Xamarin Framework would have to be updated That said, the vendor whose app we're having issues informed us this morning that Microsoft has identified the root cause and are in the process of testing a fix. I don't have a timeline or any more information than this, but it's encouraging.