Here are, as I promised, long, long time ago
ALL VDO navigation firmwares that I have, which can (not always) repair system errors, and sometimes even unbrick Your device.
Just UNRAR content, than in folder with device name You'll have ZIP archive, which should be be UNPACKED directly to EMPTY SD card.
Put it in device, restart device and wait until finished.
You'll be prompted to remove SD before restarting device after firmware upgrade.
If You messed up with unlock, it will bring You to the BEGINNING, so You can try again.
Here is content VDO Service card content
UNRAR directly to EMPTY SD card, restart device.
With it You can determine exact device model, test device, test GPS, calibrate screen, ...