My new screen keeps on glitching

Hello,

I had to replace the battery on my iPhone xs max after light water damage (the sim card tray indicator is still white). In the process of putting a new battery in, I damaged the screen which I replaced with a cheap eBay one.

Every 15 minutes or so my screen glitches out showing white and black lines (see picture at the end), but it fixes itself when I lock and unlock my phone. I have unplugged the earpiece speaker as I thought this might be causing the issue but the problem persists. Any help would be much appreciated.