I had this happen with the first airpods I bought a year ago. Had them replaced by Apple a month or two ago. Guess what, the replacements are doing the same thing. The odd thing is sometimes after listening to music on them for a couple hours, one will show it's still fully charged, while the other is down to 70%. It's not as if one wasn't working, as I could hear the music in both ears. So for some reason, sometimes it does not show the battery drains. When that happens, and I put them back in the charging case and the light stays green because one of them is still at 100%. When that happens, the next time I use them, the one that was at 100% remains at 100%, while the other dropped from 70% to less than 10%. Weird. The only way to fix that is to only charge the drained one until it gets to 100% and then place the fully charged on back in case, and then they will both remain at 100%.