Multi Touch doesn't always work Pixel 4a replacement screen

Hi,

I just replaced the screen of my Google Pixel 4a smartphone. It seemed to be running fine, but from time to time, the multi-touch feature of the screen stops working. I get stuck with single touch capability (one finger a a time). Then, after some time, it starts working again.

Using "developer options", I managed to confirm that the screen only detects one finger (while it detects up to 10 at a time when everything works fine).

It does that during continuous usage session of the phone and screen. It sometimes works fine for several minutes, and sometimes for a few seconds only.

Turning off and on again the display doesn't fix it. Rebooting the phone doesn't fix it. I reset completely the phone by reflashing the official Rom, then another LineageOS Rom, it didn't fix the problem.

What would you try to fix that ?

I fear it comes from a hardware failure. Is there a way to contact iFixIt to get a free replacement screen ?

Thanks in advance for your help.