Chosen Solution
So I have an iPhone 6S 64gb bought from eBay. The problems are: it would reboot or turn off after lock screencan’t update via iTunes(error 9), 3uTools(error -1) or even on iPhone but I can restore it.phone heats up quite fastbattery and LCD have been replace but still the same symptoms So I suspect is a hardware issue related to the motherboard but where and how much will it cost me to fix this.
Probably a failing board, you most likely need to just replace the board. For the price, its typically more worth it to just get a new device unfortunately.
