Chosen Solution

Im replacing a screen on an iPhone 7 for a friend and before closing it up I tested it twice and it was working but when I went to close it up it didn’t fit as well as it should so I took the screen off and on 3 or 4 times with no luck then decided just to close it up and put the screws in and it was fine. Turned it on and its boot looping. so I take the screen off a couple more times and no luck. I had a second screen I have for another repair coming up so I put that one on and it worked! Great! I took the home button off to align it a bit better, test it again and its boot looping. Take it off and on a few more times and no luck. I put everything back on the original screen and it works fine so I can only assume the home button and camera flex are fine as the original broken screen is an aftermarket screen I put on this phone only 6 months ago. Also if I leave the home button disconnected both screens work! If I leave the camera flex disconnected both screens work but neither work with both connected. The company I got them from said I can return them for testing (not done yet) and let me get another (that they tested and sent me pictures of it working but they didn’t have the camera flex connected when testing) but that one doesn’t work either. I am currently waiting on a replacement camera flex to try but Im not holding my breath! So the likely culprit seems the screens are faulty but for all 3 to be faulty seems a stretch and 2 of them actually worked briefly and the fact that the broken screen (aftermarket from the same company) boots fine suggests the button and camera flex are fine so I don’t know what to do and I cant afford to pull any more hair out! Any help would be greatfull and sorry for the HUGE post

No worries about the huge post but in the future, use paragraphs :>), it’s helps with the structure and makes it easier to read and follow. So if I understand correctly: The original, cracked screen (aftermarket) works fine with both the FCAM and HB.The first replacement screen boot loops when FCAM/HB are connectedThe second replacement screen, which you had on hand, does the sameThe third replacement screen, which the vendor sent and had a picture of it working, also has the same problemAll of these screen come from the same vendor but not the same batch Now a few questions: Do you know what version of iOS this phone has? Is it the newest iOS 12?Have you tried just installing either or the Home Button or FCAM to see how it affects the bootup? You’re troubleshooting seems to point to defective replacement screens. I agree that getting three bad screens seems like a stretch though. My concern here though is just how many times you have connected/disconnected the screen. It is quite possible that you damaged either the flexes, the connectors or even the logic board. Seeing as how the only good combination was the original screen fully assembled (FCAM/HB), I would go back to that configuration to see if it still works. If it does, then you probably have bad screens. If it doesn’t, then you probably did some accidental damage. Take out a magnifying glass or jewelers loupe and closely inspect the board, connectors and flexes.