I think the converted Skoda unit got judged a bit too harshly here and you probably should have just stuck with it.
Skoda is owned by VW and the hardware is fundamentally VAG anyway.
Looking through the initial faults, all of them were straightforward to resolve:
- Incorrect coding: flash VW parameter set
- Check software version management: enter new calculated hex in 5F adaptations (many calculators online for this).
- Component protection: remove with dealer software.
- DAB antenna fault: if you don’t have DAB, disable it in 5F long coding. If you do want DAB, you'll have to live with the fault as most aftermarket DAB antennas trigger this fault anyway.
- communication fault: if you don’t have sensors, disable it in 5f adaptations.
All done.
At that point the unit would have been fault free.
You probably could’ve removed 3 of the 5 faults yourself pretty easily and just lived with the remaining 2 (incorrect coding + ), as neither of those would affect the actual day to day functionality of the unit.
Also worth mentioning, if the seller was able to firmware convert the unit, they know their way around these systems. Might’ve been worth reaching back out to them for support before replacing the unit entirely.