(1) Does the error message really contain
mounting/dev/sdb4 and at/media/acc/Others1 as single words? (2) The message refers to Others1 and then you umount /mnt/Others for some reason and there is no error like not mounted, as if Others had been mounted. So something had been mounted on Others, but you wanted to mount something (maybe even something else) on Others1 and failed, so you unmounted Others. What is the connection between what you unmounted and what you wanted to mount? Why did you unmount the former at all?