What component would be causing LCD glitches?

So my friends iPhone 6 has been having these crazy intermittent glitches with the screen. Before I start with that, this phone was repaired about a year ago due to a blown back light filter/filter circuit. The phone required micro-soldering and worked fine up until now. The glitches happen intermittently. So sometimes the phone will work fine for days at a time, and then glitch off and on through out the day.

I have already tried a new screen on the phone to isolate the issue. So I know it's a mother board issue. She also said that sometimes (not often), the touch will wig out, which is causing ghost touching and random apps opening. I would assume that touch disease is responsible for that particular issue, which is very rare in the 6 model & more common in the 6 plus model. But the touch issue has only been happening since the glitching. So touch disease is some what ruled out... Especially seeing that this type of glitching is not the kind that touch disease causes.

I did happen to noticed that the heat shield that was removed to repair the back light filter was loose. I highly doubt that it's shorting out on anything, but I taped it in place to prevent it from moving around until I'm able to get it soldered in place.

Does anyone know what would cause this issue? I have uploaded a video of the issue to YouTube which can be found here. https://www.youtube.com/watch?v=XG9qVzDL...