Left Airpod dies when battery gets to 50%

I have the first generation airpods. The left airpod dies once its battery gets to 50%. This does not happen for the right airpod, which will die at 0%. Both of them will charge to 100% in the case, and they drain at about the same speed, but the dead battery noise comes out of the airpod once it hits 50% power and then it suddenly goes to 0%. I have reset the airpods twice, and it's facing the same issue.