Are you sure you aren't just using tips that are too large?
I've used AirPod Pros for the past ~3-4 years and have spent hundreds of hours walking, running, and biking with them. They have never once come out or even become loose, though I do use the smallest size tip.
Not the person you're replying to but I tried all 3 sets of standard tips as well smaller 3rd party tips and none of them sat in my ears well enough while doing any kind of moving around (or gum chewing) so I ended up giving them to a friend and going back to the standard AirPods because I've never had a problem with them staying in my ears. What's weird is that before AirPods came out my standard earbuds were the Panasonic ErgoFit ones and those always stayed in my ears no problem with the smallest set of tips.
it's a fair question - I tried using all three sets of tips. I settled on the smallest size, but even they won't stay in. I find myself wishing they were a little longer.
I've used AirPod Pros for the past ~3-4 years and have spent hundreds of hours walking, running, and biking with them. They have never once come out or even become loose, though I do use the smallest size tip.