UPDATE (9July T+23hrs):
I just got off the phone with Microsoft's Level 2 Tech support. The data loss and corruption issue is known and there is a crisis team working on a fix. Unfortunately, it seems like there may not be anything. The tech claimed it happened to him but he had backups to restore from. I was told I would receive a call back in 2 days time after he had given them more time to come up with options and see if there's anything they can do. Bottom line seems to be that having. An external backup solution is absolutely critical to using Windows now.
TL;DR - Microsoft is aware but doesn't know what to do about this.
