Left AirPod is quiet unless tilted to a certain angle.
AirPods connect and work okay, left one is very quiet but comes back to normal volume if you wear it with the bar horizontal and facing forward. You can literally rotate the bar forward, volume comes back to normal, rotate it back (so it lints downwards, as normally worn), goes very quiet. I've seen a few similar posts where the answer is cleaning, but thoroughly cleaned and no change.
Using iPhone 8 and XS.