My screen has flashes of colors

Hello,

My screen sometimes flashes with purple big lines on the screen or atifacts. I thought it was the GPU and I changed the mother board but it continues to do so. I tried with an other SSD but still the same.

When I connect an hdmi cable to have double screen with my TV, flashes and artifacts automaticaly stopped.

I’m wondering if I could have bought a new motherboard with the same problem or could I be sur now that I need to change the screen.

Thanks for your help.

Benoit