No clue to what it could be then, other than you might have a fake card that reports more space than there actually are. So unless you bought it from a trusted source, like a known store or alike, i would go do some read write tests on the card. like move a file around 25-30GB to the card and see of you can read the file without errors after transfer is complete. If you can’t, then it’s a fake, and then that’s your issue. Often they have like a 2-4GB of chip but the controller reports 32GB and the case and box it comes in looks authentic so any one can be fooled easily, ive been fooled once, lucky for me i didn’t pay much and the store i bought it in replaced it with an authentic twice the size as an apology.