Why is my phone detecting two taps instead of one on the screen?

I'm observing a strange behaviour on my phone out of the blue. Yesterday, the left side of my screen stopped working properly. I started having a hard time clicking anything next to the left edge, typing the keyboard or pressing buttons on the left. I enabled *Developer Options > Input > Show touches*, and I was able to observe that when I try to tap the left side of the screen, the screen appears to detect two taps on opposing sides of a column, as if the whole column of pixels were damaged. The phone hasn't suffered any hits or gotten wet. This is just out of nowhere. " class="img-fluid rounded" style="max-width: 100%; height: auto; margin: 10px 0;" loading="lazy"> I've uploaded a video of this to make it clearer here . This is an Xperia Z3, D6603, running Android 5.1.1. Has anyone encountered something like this? I've tried restarting the phone to no avail.