Screen problem or motherboard fault?

Hello everyone,

I’m reaching out because I’m facing an issue after replacing the screen of a Samsung A21s.

After replacing the screen, I noticed a problem with the display (see photo). The screen shows a faint checkerboard pattern across the entire surface, along with ghost images, and the touch functionality doesn’t work.

For context, the original screen was replaced because it wouldn’t turn on, although the glass was not broken.

I initially thought the issue was with the replacement screen, but even after trying another new screen, the problem persists. I also tested replacing the internal LCD connection cable and cleaned the connector, but this didn’t solve the issue.

My question is: could the problem still be with the screens (even though they are 100% original, ordered from the ASWO platform), or is it a motherboard issue?

Thank you in advance for your help and advice.