I am native too, but I think they're both correct.

Alex, I am native and I can say you are absolutely right. - Diepvriezer --> the machine - Diepvries --> the state of food. e.g. Diepvriesgroenten (frozen vegetables)

Thanks for your answers !

yo maybe i'm wrong (since i'm not a native), but 'diepvriezer' is the freezer itself, and 'diepvries' is actually the state of the food, as in - frozen food. Also google seems to be on my side, as dipevriezer always delivers results of freezers with price tags