オリジナル投稿者： Minho ,
As a shop owner, I'll safely assume that you can vouch for the good working condition of the replacement parts you tried. In that case, it's hard to say what could be causing the problem. Did the customer give you any background history of the device? Considering all of the issues with the iPhone 6S, aftermarket screens and iOS 11 (you can read more on that [https://www.refectio.ca/blog/ios11-touch-failure|here]) as well as the throttling issues Apple has admitted to (you can read on that [https://www.refectio.ca/blog/iphone-slow-throttle|here]), it sounds like it could be a lot of things. Make sure the phone is up to date, try some known-good parts (again) and see. If that doesn't solve it, then I suspect there may be a deeper issue, perhaps on the logic board.