Why does my display have a small non-working touch area?

I recently bought a display for an iPhone 5c, and managed to get the phone up and running. After some minutes of usage, I noticed there's a section of dead touch zone vertically from about where the display cables run from inside. I re-opened the phone, cleaned the connectors and the motherboard on the display, put everything thing back up and restored the iPhone. After setting it up again, the touch zone still doesn't work. The display shows everything fine, with no issues on it, color-wise or image-wise. It is just an area about 3 mm thick that seems to not respond to touch. I ordered a brand new display, and installed in the same exact way, but I'm still getting this issue. Any ideas would help! Please and thanks :(