I guess this is very individual, and depending on the tip (size/material), but for most of the tips I've tested now... this is difficult to live with.
Tried to google "Devialet Gemini driver flex", and found some hits.
So I guess it's nothing wrong with my set, since several people hear it too.
From Stereonet:
https://www.stereonet.com/reviews/devialet-gemini-true-wireless-earbuds-review
"Upon initial insertion, there's a cringe-inducing driver flex noise, a sort of scrunching paper sound. It doesn't appear to cause any issues with sound quality, but one can't help but wonder about driver longevity if this is an ongoing issue."
I don't have this with just insertion, but everytime I chew/move my mouth... I hope I find a foam tip that sounds good, or I will sell these quite quick...