Chosen Solution
I had my iPhone 6 Plus screen replaced which included the digitizer. It worked well for the first 2-3 days but then stop responding to my touch input. It suddenly starts working SOMETIMES if I press the top right part of the glass and then unlock the phone and keeps working normally the display turns off. as soon as i close the screen back to black and unlock the phone the touch stops working.
Defective screen. I can post a guide and a list of parts. However you’re gonna want to go back to where you had it repaired, and get a warranty
