I got a solution and no need to fix the original screen. it worked on my iPhone 6. and my friend's iphone 6s I had the same issue. Changed my screen and iphone 6 wont update to ios 11 and would give the error [56] at the end of the update. Went to apple store and they said hardware glitch and replace the phone for $149. The apple genius's computer gave multiple bullet points as in why this is happening, one of which was unauthorized screen /hardware changes. The solution is remove the sim and update. The phone will update to ios 11 without any issues. Sometimes dont insert even the sim tray. the phone will update alright, issues like touching on reset on the phone will make phone unresponsive, apps like lyft and turo will launch and crash back to home screen after 5 mins. Still looking for solution to that though...