Pro 3 rattle in left pod only

AirPods Pro 3, absolutely brilliant overall, but not for running.

Right pod works fine, sat still, walking, running. Left pod when running clicks and rattles when I run. Acoustic seal tells me both pods are properly located in my ears (and sounds right too).

I tired twisting the left pod in my ear to tighten the connection between the tip and the pod, and this works for a short while, after which the clicking/rattling returns. I tried different tip size, changing from medium to large, but makes no difference (and large feels too big, small is too small).

The right pod works so well under any circumstances, the left is such a disappointment when I run. I went through tech support, had the original left pod replaced, and the new one is better, but after careful placement in my ear, still rattles!

Any ideas....??