Suddenly a white vertical line.

Hello. My wife just brought me her beloved A71. As shown on the pictures it has a white vertical line.

She swears to haven't dropped the phone or had any accident. She was using it and the line appeared.

I have tried to restart, no changes.

It seems that the pixels are always on. If I remove the always on display, the line disappears. But reappears when I unlock the phone.

Any ideas?