files disappear upon umount

I have a mystery ... a reproducibile one, but still a mystery. My ideapad 100s has a SD card reader which I use to store stuff while I work on it, as its built-in drive is super tiny. Its really just a temporary use, because I normally git push stuff quite frequently. This has worked for sometime, but now stuff that I add to this SD card filesystem disappears at the time of umount. All the files I did put before are still there, it's just the new stuff that disappears. It happens all the times I do umount. I have tried to issue sync . in the new folder, I have also tried to change a bit the fstab line for this SD card, but cannot solve this. I noted that in dmesg there is a message about the filesystem

[Sun Dec 10 19:34:48 2023] EXT4-fs (mmcblk1p1): warning: mounting unchecked fs, running e2fsck is recommended
[Sun Dec 10 19:34:48 2023] EXT4-fs (mmcblk1p1): mounted filesystem without journal. Opts: (null)

and I did try a simple e2fsck and it insists that it was not cleanly unmounted even after repeating.

sudo e2fsck /dev/mmcblk1p1 
e2fsck 1.46.2 (28-Feb-2021)
/dev/mmcblk1p1 was not cleanly unmounted, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/mmcblk1p1: 18783/15622144 files (0.1% non-contiguous), 17101516/62459904 blocks

The exit code is 1, which means it has corrected errors according to the man page of e2fs. Any idea what I am doing wrong here?