Hi guys,
I am having the same problem. I have an iPhone 5c that is stuck in DFU mode and doesn't reboot properly. The strange thing is that it's like dead when connected to my Macbook Pro 2016 (using original USB-C to Lightning cable), but when connected to power, it turns on and reboots constantly on the apple logo.
I tried the following things without success:
- booting it up attached to the current and with the battery disconnected
- changing motherboard with another iPhone 5c.
- connecting the battery of an iPhone 5s instead of the (maybe dead) original one
- connected to my Mac without screen
- changed the original, cracked screen with an aftermarket one
- changing Mac with different macOS.
Needless to say that I let i charge up for while before doing everything and that the ports on my macbook are working (tried all 4 of them).
I really don't know what it could be. Maybe a faulty flex cable or the lightning port?