wudump seems to corrupt SD card FAT32 filesystem

[JohnVeness]

Hi. Thanks for this great tool.

Every time I dump a game and move my SD card to my PC, I have to repair the FAT32 filesystem. See:

fsck from util-linux 2.36.1
fsck.fat 4.2 (2021-01-31)
FATs differ but appear to be intact.
1) Use first FAT
2) Use second FAT
[12?q]? 1
Free cluster summary wrong (330184 vs. really 295496)
1) Correct
2) Don't correct
[12?q]? 1

*** Filesystem was changed ***
The changes have not yet been written, you can still choose to leave the
filesystem unmodified:
1) Write changes
2) Leave filesystem unchanged
[12?q]? 1
/dev/mmcblk0p1: 1517 files, 1652987/1948483 clusters

Checking the filesystem after doing the above, it's fine.

My SD card (Sandisk Extreme 64GB microSD) seems OK in general. It doesn't matter which game I dump, it always happens.

As I test, I booted my Wii U (with the SD inserted), ran Homebrew Launcher, ran wudump, and pressed the button to dump to FAT32 SD. When the app said to insert a disc, I pressed Home to exit the program, and then shut down the Wii U. Checking the SD in my PC after, it hadn't corrupted. So it seems to be only when actually writing to the SD.

Any ideas? Thanks.