I have several of these cards in 64GB and 32GB sizes. But only one of these constantly gives me trouble. Popping a card into my MacBook Pro to tranfer files to another drive, all but one can take 10GB worth of files and copy them over in about 3 1/2 minutes. The bad 64GB card will take the inverse of that: 10GB copies in 30 minutes. Or 4GB copies in 12 min.
Checking “Info” on the cards shows they’re all formatted exactly the same: MS-DOS (FAT32). This always happens with this one card.
Thoughts? Is there a warranty? Could this just be a mis-labled card and not really the SD XC?