fsck.vfat 从不真正修复任何东西

我有一个用 FAT32 格式化的稍微有点乱的 64GB USB 驱动器，我想在 Ubuntu 18.04 上修复它。

第一次尝试：

$ sudo fsck.vfat /dev/sdc1 
fsck.fat 4.1 (2017-01-24)
FATs differ but appear to be intact. Use which FAT ?
1) Use first FAT
2) Use second FAT
? 1
Reclaimed 4221 unused clusters (138313728 bytes).
Free cluster summary wrong (1484695 vs. really 1488915)
1) Correct
2) Don't correct
? 1
Perform changes ? (y/n) y
/dev/sdc1: 20 files, 402763/1891678 clusters
$

但是，当我之后重新安装驱动器时，损坏的文件再次出现并拒绝任何删除它们的尝试。我可以根据需要多次重新运行命令，结果完全相同。

第二次尝试，基于如何修复损坏的 FAT32 文件系统：

$ sudo fsck.vfat -w -r -v -l -a -t /dev/sdc1 
fsck.fat 4.1 (2017-01-24)
Checking we can access the last sector of the filesystem
Boot sector contents:
System ID "THREES  "
Media byte 0xf8 (hard disk)
       512 bytes per logical sector
     32768 bytes per cluster
        32 reserved sectors
First FAT starts at byte 16384 (sector 32)
         2 FATs, 32 bit entries
   7567872 bytes per FAT (= 14781 sectors)
Root directory start at cluster 2 (arbitrary size)
Data area starts at byte 15152128 (sector 29594)
   1891678 data clusters (61986504704 bytes)
63 sectors/track, 32 heads
        63 hidden sectors
 121097025 sectors total
FATs differ but appear to be intact. Using first FAT.
Checking file /
[...]
Checking for bad clusters.
Reclaiming unconnected clusters.
Reclaimed 4221 unused clusters (138313728 bytes) in 1 chain.
Checking free cluster summary.
Free cluster summary wrong (1484695 vs. really 1484694)
  Auto-correcting.
Performing changes.
/dev/sdc1: 21 files, 406984/1891678 clusters

结果相同：fsck 发现错误，就像修复它们一样，但文件系统之后似乎完全没有改变，所有损坏的文件仍然存在。

当然，文件系统在 fsck 之前已被卸载。我错过了什么？