Mkdir creates file instead of directory on windows network drive mounted as drvfs using Ubuntu/windows 10 under WSL - linux

Question

The command mkdir creates a file rather than a directory on a mounted network drive on a windows 10 system operating under the Windows sub-system for linux, using the Ubuntu app.
After installing the ubuntu app and putting the windows machine into developer mode I successfully mounted a remote network drive using the command:
sudo mount -t drvfs '\\networkdrive\sharename' /mnt/U
which successfully mounts the network drive at the mount point. I can see the files on the remote drive. However when looking at a directory on the remote machine and issuing the command
mkdir Source
a file called Source is created on the remote drive rather than a directory.
I tried this on two completely different laptops running windows 10, which I set up in exactly the same way and the same problem happens. The windows 10 machines are in developer mode and running the latest version of the ubuntu app. This is a pretty fundamental thing to have go wrong so I'm guessing it's a bug of some sort.
The snippet below is the terminal output which illustrates the problem.
username#~$ pwd
/home/username
username#~$ sudo mount -t drvfs '\\networkdrive.host\sharename\' /mnt/U
[sudo] password for username:
username#~$ cd /mnt/U/People/username/projects/Vesiform
username#Vesiform$ ls -al
total 0
drwxrwxrwx 0 root root 512 Mar 29 2018 .
drwxrwxrwx 0 root root 512 Mar 28 12:04 ..
drwxrwxrwx 0 root root 512 Mar 28 11:12 Builder
drwxrwxrwx 0 root root 512 Mar 28 11:42 Library
drwxrwxrwx 0 root root 512 Mar 28 11:42 NPack
drwxrwxrwx 0 root root 512 Mar 28 11:42 PDBProc
drwxrwxrwx 0 root root 512 Mar 28 11:55 Projects
drwxrwxrwx 0 root root 512 Mar 28 11:55 SpacePack
drwxrwxrwx 0 root root 512 Mar 28 11:55 Utilities
username#Vesiform$ mkdir Source
username#Vesiform$ ls -al
total 0
drwxrwxrwx 0 root root 512 Mar 29 2018 .
drwxrwxrwx 0 root root 512 Mar 28 12:04 ..
drwxrwxrwx 0 root root 512 Mar 28 11:12 Builder
drwxrwxrwx 0 root root 512 Mar 28 11:42 Library
drwxrwxrwx 0 root root 512 Mar 28 11:42 NPack
drwxrwxrwx 0 root root 512 Mar 28 11:42 PDBProc
drwxrwxrwx 0 root root 512 Mar 28 11:55 Projects
-rwxrwxrwx 1 root root 0 Mar 29 2018 Source
drwxrwxrwx 0 root root 512 Mar 28 11:55 SpacePack
drwxrwxrwx 0 root root 512 Mar 28 11:55 Utilities
username#Vesiform$ cd Source
-bash: cd: Source: Not a directory
username#Vesiform$