sudo dosfsck -a /dev/sdb1
fsck.fat 3.0.26 (2014-03-07)
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
 Automatically removing dirty bit.
FATs differ but appear to be intact. Using first FAT.
/PVR/TEMPTEST.SPD
  File size is 1 bytes, cluster chain length is > 4096 bytes.
  Truncating file to 0 bytes.
Free cluster summary wrong (764153 vs. really 764154)
  Auto-correcting.
Performing changes.
/dev/sdb1: 5 files, 180333/944487 clusters
Writing 512 bytes at 0 failed: Operation not permitted
Writing 3777956 bytes at 3794432 failed: Operation not permitted
Writing 4 bytes at 737716 failed: Operation not permitted
Writing 4 bytes at 4515764 failed: Operation not permitted
Writing 4 bytes at 737720 failed: Operation not permitted
Writing 4 bytes at 4515768 failed: Operation not permitted
Writing 4 bytes at 1000 failed: Operation not permitted