I had the issue where sometimes only one was charged. I noticed that sometimes the LED didn't blink when inserting one of them... and fidgeting with it, helped, but sometimes switching the position of the case from vertical to horizontal would make it disconnect (as reported by the charge widget on my iPhone).
(I tried resetting them, re-pairing, etc. and it didn't help)
I took it to the Apple store, showed the guy the issue, and he claimed it was most likely a firmware issue and not the case. He said the Airpod disappearing from the charge widget was the firmware misreporting, and not a bad/loosy connection. I had my doubts and was sure that it was a physical issue with the case... but he replaced the single airpod (he updated the new one's firmware first) and the issues went away.
(I tried resetting them, re-pairing, etc. and it didn't help)
I took it to the Apple store, showed the guy the issue, and he claimed it was most likely a firmware issue and not the case. He said the Airpod disappearing from the charge widget was the firmware misreporting, and not a bad/loosy connection. I had my doubts and was sure that it was a physical issue with the case... but he replaced the single airpod (he updated the new one's firmware first) and the issues went away.