Touch screen only works when back is off...

I just bought a replacement screen and it worked for 2 days and is now unresponsive. I just found something very interesting in troubleshooting it. If I leave the back cover off, the touch screen works perfectly, if I put the cover on, the screen does not respond to touch. I have checked for damage, bad seating, areas that may be applying pressure to components, I see nothing wrong at all. I did notice a few areas of electrical contact between the back cover and the main board so maybe something is grounding out for some reason but I do not see this occurring. Anyone ever run into anything like this?