Right Airpod Fails When Outdoors

I have 2nd generation airpods. When I am using them outside, fully charged, after 10-15 minutes I get the "out of charge" sound in the right airpod, and the audio in that side stops. I put it back in the case and close the lid. Take it out again nearly immediately, and it is fine again. The iphone they are connected to show both pods fully charged. This happens every every five minutes or so.

This never happens when I am using them indoors. Indoors their behavior is exactly as expected. I have reset them several times. Anyone have an idea?

TIA