> *** Error in `ntfsfix': free(): invalid pointer: 0x00007f733989b678 ***
This is caused by retrying a failed umount before leaving ntfsfix, and the attached patch should fix this bug. The failed umount is a consequence of not being able to write to /dev/sdk1, and IMHO this is caused by some hardware error. As ntfsfix finds no error, you should be able to mount the device read-only.
ntfsfix-unmount.patch.gz
Description: application/gzip
