Downgrade from 6.0.4 to 6.0.3

-Download the files you find  here 

-Unzip and get the file .lgu in USB flash drive (I recommend it, format it to FAT32 else is not recognized)

-Install it in medianav as any update.

Downgrade from 7.0.5 or 8.0.5 to 6.0.3

• Download the files you find here
• Unzip and get the file .lgu in usb flash drive (fat32 formatted)
• install it in medianav as any update