Cannot restore iPhone 5s due to iTunes error 9

I had a friends iPhone 5s 16gb (C-Spire) on iOS 10.2.1 for a while. I swapped out the logic board temporarily with another friends 5s to see if it still worked. When putting the original logic board in a day later, the phone was stuck in a bootloop. It shows the apple logo for about a minute & restarts again.

Even worse, whenever i try to restore/update the device via iTunes, i always get error 9. I've tried multiple computers/cables, i tried dfu & pwned dfu mode, i even went to the apple store where they said they couldnt help me after they got error 9 a few more times.

I read some really old threads on how to fix iPads by using i4 tools, but that didn't seem to do anything for me. Any 3rd party program i try to restore with usually gets stuck at about 20%

Dont really care about whats on the phone at this point, is there a way i can make it function again?