I have a 1TB SanDisk XC SD card, which has developed a reluctance to
create files.
UUID=0fd984c4-cf88-408a-8ba5-15b64500bd5c /Media/SDXC ext4
noauto,rw,user 0 0
% sudo mount /Media/SDXC
% touch /Media/SDXC/foo
% ls /Media/SDXC/foo
/Media/SDXC/foo
% sudo umount /Media/SDXC
% sudo mount /Media/SDXC
% ls /Media/SDXC/foo
/bin/ls: cannot access '/Media/SDXC/foo': No such file or directory
I used root to mount, just to be sure. User mount has the same problem.
gparted reported a problem with the superblock which was resolved by
re-formatting and re-creating the partition table. The card has just
one partition.
Suggestions for further diagnosis would be appreciated.