Mercedes sprinter usb/sd card

[steve Wilde]

I Have a Mercedes Sprinter 313 64 Plate and i am having problems with the USB and Sd card playing music i have down loaded same songs on both sd and usb (both 32gb) but both usb and sd card will not let me see or play all the contents only about 1/2 of what is on both ??? is there a limit to what they can read on the system does anybody know what problem is thanks Steve