According to Apple Error 53 is related to the touch ID sensor. If the sensor or any part of the assembly is damaged, fixed or replaced by non-authorized Apple technician, the fingerprint data uniquely paired with the touch ID becomes invalid. Once you do an OS update or have to do a restore on the phone, where the paring needs to be valid, you phone can throw the error 53. If that happens, chances are your phone is no longer usable and needs to be replaced. Apple recommends contacting their support if the error pops up.