I have a 64GB Ultra MicroSD card which has been working fine in my phone for a year or so.
Recently the phone has been acting a little strange, and I’ve tracked it down the the MicroSD card - it seems to be unable to hold on to anything I write to it.
I can save a file to the card, and read the file perfectly well while the card is still mounted. If I unmount the card and remount it, the file is gone. The same with deletions, and even formatting. I can do a full NTFS format (not a quick format) and the card appears blank, and I can save new data to it, and read it. If unmount the card though, it’s back to the state before the format - I can read all the files on it too.
The only thing I can think of is that the file allocation system is corrupted somehow.
Really strange. Have I just managed to get the card into a read-only format, or is it broken?
Also, I’m not using an SD-card adapter. I have it in my phone and have the phone connected via USB in data-transfer mode.