Replaced Front Face Assembly, Touchscreen Only Works When Opened

I replaced the touchscreen on my iPhone 6 about a month ago (actually, the whole front assembly) and it (the touchscreen) will be responsive when my device is open. But, whenever I put back the screws and cover plates and close the phone, the touchscreen is unresponsive. Over time, I opened it multiple times, replacing the screws, one at a time, to see if that was the problem. Nope. Same problem. When open, it works; when closed, it stops working. Frustrated, I put the phone away. Yesterday, I opened the phone and moved the screen a bit without disconnecting anything (not the cover plates or the cables) and the touchscreen responds. I close it, it is unresponsive.

This is the second screen I purchased. I had the same problem with the first assembly and returned it. When I replaced it with the second one, it didn’t make sense to me to return it because the part does work but for some reason, every single time I close up the phone, the screen doesn’t respond. The front facing camera works, the home button works when the device is closed. It’s just the touchscreen that doesn’t work when closed.

An iPhone isn’t supposed to be open with its guts exposed to work. I thought about keeping the cover plates off for the battery and front assembly cables but, in my mind, these parts serve a purpose and make me leery that the phone will malfunction even more so than before so I put them back where they’re supposed to be. What could be the problem? Any assistance will be appreciated. Thanks.