I had the same issue. I found this page about resetting AirPods to Factory Default. So far so good.
https://gearpatrol.com/2017/04/03/factory-reset-apple-airpods/
1. Go to Bluetooth settings on your device. Forget your AirPods.
2. Make sure both AirPods are in their case. Open the lid so you can see the indicator light.
3. Hold the button on the back of the case until the light starts flashing amber. (Some Apple forum threads say this should take 3–5 seconds, but on my AirPods it took about 15 seconds.)
4. After the amber light blinks three times, release the button and close the lid.
5. Place your AirPods adjacent to your iPhone and hold the button on the back of the case again. A pairing screen should appear on your iPhone. Press “Connect” and you should be good, with both AirPods should work properly together again.