D-Fly and Edge 520 don't play nice together?

My Edge 520 and EWWU111 don't want to work together. I've had them both for about a year. Periodically, the 520 seems to lose the D-Fly and reconnect - like every 30 seconds. This really drains the battery on the Edge fast. Doing a full reset of the Garmin helps, but the problem crops back up after a few weeks. Now it's happening all the time and a reset doesn't seem to help.

Firmware is up to date on everything. Does anyone know if there's an issue with the Shimano D-Fly and Edge 520?