Comment 2 for bug 196075

"...in the attempt of obviously (as reported by df) mounting several existing ntfs partitions from my drives into one mounting point (/var/lib/os-prober/mount) for whatever reason (looks like some known issues in mount.ntfs-3g 1.913...)."

This is os-prober trying to determine what operating systems are on the partitions on your disk. This is not a bug.