iPhone 6 Screen Replacement Backlight Issues

My screen on my iPhone 6 had been cracked for awhile so I decided to replace the screen. I have been replacing screens for a long time and this is probably the 5th or 6th screen that I've put on this device. I ordered a screen off of Amazon and replaced it how I normally would. However, on this screen, I noticed that one of the flex cables had a little piece of transparent tape that held it so it would be facing the incorrect direction in order to install it. Subsequently, I removed this film and saw that it seemed to be exposed ribbon cable. Not having ever experienced this issue, I thought nothing of it and replaced the screen like normal. The phone worked fine for a couple hours, then seemed to go completely black and would only return to working properly if I applied pressure to the bottom right hand corner of the screen. After a few hours of this working, the screen was permanently stuck on about 1% brightness. When I returned home, I reinstalled the old cracked screen and things pretty much went back to normal, except that the phone flickers a little bit and brightness only works between the normal lowest brightness setting and about 25% (everything above 25% looks the same).

I have looked at a variety of other forums and have seen that this unprotected cable could have caused a short in the backlight of my phone and would have to be re-soldered in order to fix the phone; however, this doesn't exactly explain why the old screen is still working and why the brightness is not working completely normally. What else could possibly be done to fix this issue?