Normally As known the iPhone touch screen comes from three different factories : TOSHIBA /LG / SHARP. How to recognize the brand of iPhone LCD, Please refer to it as below.
Toshiba LCD Screen: The beginning of the code of the backlight of the phone is C11, F7C
LG LCD Screen: The beginning of the code of the backlight of the phone is DTP，C3F
SHARP LCD Screen: The beginning of the code of the backlight of the phone is DKH，C0N
But in the actual maintenance process, the Sharp screen on the iPhone7/7P is very rare, in other words, Mostly the touch LCD screen from both Toshiba and LG of the two factories.
If the original iphone screen of the iPhone 7 PLus come from Toshiba factory, then you need to find the Toshiba screen to replace, Boz if use LG brand LCD, there will be no touch problem. Even go to repair store for repairing the iphone 7P, still unable to fix it
So. same way, If the old iphone 7P with LG brand LCD screen,then use same brand to replace the screen then.
Therefore, in the future when changing iphone LCD screen of the 7 Plus, please be sure to check the code on the backlight, which could greatly reduce the problem of touch function failure.