Why does my left AirPod keep disconnecting

Hello:) Give this a try:

Try a full re-pair, reset, and try again.

Start with Unpairing/"Forgetting" the Device:

Settings > Bluetooth > Airpods > Forget this device. Confirm it.

Put both Airpods in their case, charge them via Lightning for a few minutes (or preferably until the case is 100%). Unplug them. Open the case and hold the button on the back of the case for 15+ seconds or until the light flashes white. Hold them near your iPhone and see if the pairing screen comes up and pair them. If not, repeat until it does. But if you can't see the screen pop up, then manually pair within Bluetooth.

~Katana-San~

Hello again:) Sorry for you frustration so maybe need cleaning?

https://support.apple.com

Web results

How to clean your AirPods, AirPods Pro, AirPods Max, and EarPods - Apple Support

Since you know without a doubt what you are doing with these you may want to contact Apple Support for further help and replacement of one or both. Could even be the case...have you reset it as well? Good luck.

Hello again:) You have done all the things I myself would have done for sure. I would at this point go to upper right and click on Get Support and go from there. Good luck.

~Katana-San~

Hello:) You are very welcome.

~Katana-San~

Ditto. Still keeps dropping. Apple will only offer me an out of warranty replacement for $69.

Hello again:) Glad to see you are happy with your new Airpod pro's. Hope to see you here in the forum often.

~Katana-San~