Artefacts in pictures taken from any camera (front or rear)

Hi all,

I have a very weird issue.

When I take photos, I have multiple artefacts (colored dots : Green / Pink / ...).

It depends on the light and the vividness of colors taken.

In live pics, only the key pic has dots, none of the others. That means, if I edit the live pic, and select another pic to be the key one, the dots are not showing.

Using another app, like LightRoom, doesn't make this issue in DNG, but only in JPG.

When taking videos there's no issue...

This problem happens using any of the cameras (both rear, or front one)...

Sometimes, if I take the picture and I watch it quickly, I can see some dots disappearing.

If I send the picture to another device (not necessarily one of mine), the dots are still visible.

I have factory reseted... Used without any apple ID... DFU + restored new firmware...

Apple Store Staff think this is hardware issue, but in the diag they did, there is no evidence of that...

The phone works pretty well for anything else.

It doesn't get hot, Geekbench and 3D mark gives good performances, no glitches in any video or 3D games...

My phone has less than 2 years, I am supposed to have vendor's warranty, but the vendor is not reachable.... Phone doesn't work, emails are not delivered (mailer deamon)...

I really don't know what to do ! And over all I'm pretty sure this could be fixed by software patch...

Thank you all in advance for your help.

Francois