Error 29 = battery problem. Error 28 = faulty charging port. Both are hardware errors.
Error 29 — battery
Appears after battery replacement with non-certified part, or when original battery is completely dead and can't hold enough charge to complete a restore.
Fix: Replace with certified battery → ensure connector properly seated → retry restore.
Error 28 — charging port
Charging port pins corroded, bent, or damaged. iTunes can't maintain stable USB connection even if charging seems to work intermittently.
Fix: Charging port replacement — usually done in under an hour.
If none of the above works, the issue is most likely physical hardware damage — a failing chip, corroded connector, or broken internal component. If you've tried everything above and the error keeps coming back, the problem is most likely physical — something broken inside the device that software can't fix. That's when it needs professional hands-on inspection.