Finch reports a spike in the UMA notification: Stability.BadMessageTerminated.Content on stable channel, for the bucket SWDH_UNREGISTER_CANNOT, on Android+Mac+Windows+CrOS.

Graph: https://goto.google.com/cavwg

This spike coincides with the M51 push. Assuming M50->M51 push is the cause, the rate of these kills seems to be 3x to 10x more prevalent on M51

The overall rate is still quite low, which may be why we hadn't noticed the regression on beta.