Why is part of my replacement screen unresponsive?

I recently replaced my Moto G's screen with one I found on Amazon.com. For awhile (about 48 hours) it was working flawlessly. Then it started misbehaving. I noticed the touch screen responding poorly. I narrowed it down to one horizontal section of the screen just under the center as unresponsive. I downloaded a touch-test app and confirmed this was the case. However, this is not a permanent condition, as the area sometimes works randomly and other times is completely unresponsive.

Thinking it might be a loose connection, I took my phone apart again and checked the connections. I took the ribbon cables out and put them back in again after cleaning with alcohol. The problem persists.

What could be causing this dead section of my touch screen? And is there a way to fix it?