Shows error 9 on iTunes Restore

This is a belated answer so hopefully it can be of use to folks who search for and find this question.

Error 9 on the iPhone 6 is either a NAND or CPU issue. Beyond the usual "update iTunes, try new cables and computers", iTunes Error 9 can be either CPU or NAND related. This can be caused by multiple drops over the years.

Either way, these are advanced micro-soldering repairs, especially the CPU repair. Basically, it consists of grinding down the CPU package until you have access to some deeply embedded copper pads so that the connections can be restored to the EEPROM.

Suffice it to say that this is not a DIY repair and one which very few micro-solderers can accomplish. The NAND repair, while advanced, is more straightforward. If you want to have it repaired, contact some micro-soldering repair shops and ask them if they have successfully repaired Error 9 before sending them your phone. You don't want someone mucking up the CPU on YOUR device, especially if you need to recover the data.