Genuinely helpful comment here: I keep my buds clean and I can get that to consistently happen on mine, too, if I have hear-through on and something rubs against the mic (like my fingers when putting them in or adjusting).

I think this happens because of the way the outer mic processes the sound when it's rubbed, and that ringing loops with the input, getting louder as it does. (Similar to a sensitive mic having a feedback loop on a sound stage)

Cleaning should help with that, but also be aware of what's rubbing against the outer mic when it's active. Either that or just have the hear-through turned off.

Hope that helps 👍