Samba server issue with mount point being owned by root instead of 'force user' specified in smbd.conf

I've created a samba share on an ubuntu server called teslausb with the following lines specified in smbd.conf:

   [teslausb]
   comment = John's home share on Ubuntu
   path = /mnt/sdb1/teslausb
   browseable = yes
   writeable = yes
   valid users = john
   write list = john
   force user = john
   force group = john

john:john is the owner of /mnt/sdb1/teslausb and I've set permissions as chmod -R 755:

john@docker:/mnt/sdb1/teslausb$ ls -al
total 1600
drwxrwxr-x 2 john john    4096 Oct 18 14:17 .
drwxrwxr-x 4 john john    4096 Oct 18 02:38 ..
-rwxrwxr-x 1 john john    4096 Oct 18 03:20 ._10.11.12.11-netconsole.log
-rwxrwxr-x 1 john john 1608971 Oct 10 14:55 10.11.12.11-netconsole.log
-rwxrwxr-x 1 john john    2653 Dec 13  2016 avrflash
-rwxrwxr-x 1 john john    4096 Oct 18 02:39 ._.DS_Store
-rwxrwxr-x 1 john john    6148 Oct 18 02:58 .DS_Store

When I connect to the share via Windows, there's no problems writing to the share, however, when I mount the share on an Ubuntu box sudo mount -t cifs -o user=john //docker/teslausb /mnt/teslausb/, I can't write to the mounted share. I get a 'permission denied' error message.

For some strange reason, the mounted share also shows root as being the owner of the files in that share despite 'force user' being specified in the smbd.conf.

john@vm-ubuntu:/mnt/teslausb$ ls -al
total 1596
drwxr-xr-x 2 root root       0 Oct 18 14:17 .
drwxr-xr-x 6 root root    4096 Oct 18 12:25 ..
-rwxr-xr-x 1 root root    4096 Oct 18 03:20 ._10.11.12.11-netconsole.log
-rwxr-xr-x 1 root root 1608971 Oct 10 14:55 10.11.12.11-netconsole.log
-rwxr-xr-x 1 root root    2653 Dec 13  2016 avrflash
-rwxr-xr-x 1 root root    4096 Oct 18 02:39 ._.DS_Store
-rwxr-xr-x 1 root root    6148 Oct 18 02:58 .DS_Store

If I mount the share and specify uid and gui in the mount command sudo mount -t cifs -o user=john,uid=john,gid=john //docker/teslausb /mnt/teslausb/ I can write to the samba share but I'm trying to avoid having to specify this in the mount command and thought that by using 'force user' this should achieve the same result.

I've also tried chmod -R 777 to the samba share but this didn't help.

I'm a little confused about how this should work. Why is this share being mounted with root as the user? Can someone please help me? Thanks in advance for any help, I really appreciate it.