I see that this is an ongoing problem. I recently too, came upon the same problem in my left AirPod Pro. I thought maybe it was from listening to music too loud, or maybe water had transversed inside. But I never get it close to water and I only clean the AirPod cushions and not the AirPods themselves.
And being a musician, I always apply the credo K. I. S. S.
With that said, all I did was change the AirPod Pro cushions to another set. And Voila, the problem was corrected.
I am assuming that if there is not a tight air fit and there is any type of ambient noise getting into your ear canal. It causes feedback to either the right or left AirPod Pro.
I truly hope this solves your problem, it did for me.