I have same problem![br]
I changed my screen replacement and battery, after this operation was succesfull the device.[br]
But after while i did software update, it is crashed i mean the system trying rebooting all the time but nothing else. [br]
I did it with itunes connection, i called the apple support but they didn’t helped what is the problem. I don’t remember the error code, but my phone can’t boot.[br]
I turned off the find my phone and logout from device.[br]
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The flash with 3uTools it’s going to 19% and over.[br]
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Anybody help?