File system check failing to run on HDD in my Zgemma H7S.

[BrianG61UK]

login as: root
root@zgemmah7.lan's password: 
root@Zgemmah7:~# 
root@Zgemmah7:~# 
root@Zgemmah7:~# 
root@Zgemmah7:~# 
root@Zgemmah7:~# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/mmcblk0p8            2.2G    435.9M      1.7G  20% /
devtmpfs                145.7M      4.0K    145.7M   0% /dev
tmpfs                    64.0K         0     64.0K   0% /media
/dev/mmcblk0p1            3.0M     18.0K      3.0M   1% /boot
tmpfs                   501.8M    168.0K    501.7M   0% /var/volatile
/dev/sda1               930.4G    788.7G    141.7G  85% /media/hdd
root@Zgemmah7:~# 
root@Zgemmah7:~# umount /dev/sda1
umount: can't unmount /media/hdd: Device or resource busy
root@Zgemmah7:~# umount -f /dev/sda1
umount: can't unmount /media/hdd: Device or resource busy
root@Zgemmah7:~# umount -fl /dev/sda1
root@Zgemmah7:~# 
root@Zgemmah7:~# ls /media/hdd
root@Zgemmah7:~# 
root@Zgemmah7:~# fsck.ext4 /dev/sda1
e2fsck 1.46.5 (30-Dec-2021)
/dev/sda1 is in use.
e2fsck: Cannot continue, aborting.


root@Zgemmah7:~# fsck.ext4 -f /dev/sda1
e2fsck 1.46.5 (30-Dec-2021)
/dev/sda1 is in use.
e2fsck: Cannot continue, aborting.


root@Zgemmah7:~# fsck.ext4 -fv /dev/sda1
e2fsck 1.46.5 (30-Dec-2021)
/dev/sda1 is in use.
e2fsck: Cannot continue, aborting.


root@Zgemmah7:~# fsck.ext4 -v /dev/sda1
/dev/sda1 is in use.
e2fsck: Cannot continue, aborting.



root@Zgemmah7:/# fsck.ext4 -vn /dev/sda1
e2fsck 1.46.5 (30-Dec-2021)
Warning!  /dev/sda1 is in use.
Warning: skipping journal recovery because doing a read-only filesystem check.
/dev/sda1 has been mounted 236 times without being checked, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Free blocks count wrong (37145051, counted=37141905).
Fix? no


        3596 inodes used (1.01%, out of 357744)
         651 non-contiguous files (18.1%)
           3 non-contiguous directories (0.1%)
             # of inodes with ind/dind/tind blocks: 0/0/0
             Extent depth histogram: 2598/989
   207045157 blocks used (84.79%, out of 244190208)
           0 bad blocks
         126 large files

        3578 regular files
           9 directories
           0 character device files
           0 block device files
           0 fifos
           0 links
           0 symbolic links (0 fast symbolic links)
           0 sockets
------------
        3587 files
root@Zgemmah7:/#
root@Zgemmah7:/#

he only way I can seem to get fsck running is with -n and as I understand it that means the result is largely meaning less.