Make a backup of a navi-sd card?

Hi everyone,

I will make a clone of a navi-sdcard for backup from the original.
I can copy the card but the copy will not work.
I have copy the master-sd-card to a empty sd-card.
Thats no problem but the Discover media plus - device from VW don't recognize that card.
Someone says to me that it's is because there is a hidden secured partition on the SD-card ?
anyone here experience to read/view hidden secured partition on a SD-card?

Timm.