iPhone 7: Error 53 after screen replacement (iOS 12)

Hi everyone. My iPhone 7 fell on the floor and the screen got smashed so bad it stopped displaying the image. Lickily, I had a perfectly working iPhone 7 lying around, so I just swapped the whole LCD assembly. The display turned on and displayed the restore required image. But, when I tried to restore, it would stop halfway and then produce the dreaded old error 53. Why is that? I tried DFU restore, replacing the battery, unhooking the rear cam and all combinations thereof. Please help.