Have you tried just pairing them again like-new? As in put both in one case, close it, open it, and hold the sync button until it glows white?

I've personally lost more Airpods than I want to admit and now have roving pairs of unpaired AirPods in my apartment, which I randomly re-pair when I'm in a hurry and don't want to find the correct pair.

I'd imagine that's as much of a torture test for the pairing system as could exist and it still works...