Files in a host mapped volume aren't recognised

On the server, create a temp dir with a txt file in it:

[dc2dmat05]: PS C:\> mkdir temp

    Directory: C:\

Mode                LastWriteTime         Length Name                                                                                                         
----                -------------         ------ ----                                                                                                         
d-----       14/08/2017   8:17 AM                temp                                                                                               


[dc2dmat05]: PS C:\> cd temp

[dc2dmat05]: PS C:\temp> echo 'This is a test!' > test.txt

[dc2dmat05]: PS C:\temp> type .\test.txt
This is a test!

[dc2dmat05]: PS C:\temp> 

Use my (Win7) workstation to create an interactive tty session:

C:\tmp
λ $env:DOCKER_HOST='DC2DMAT05:2376'
C:\tmp
λ docker run -it -v C:/temp:C:/temp microsoft/windowsservercore-insider

Microsoft Windows [Version 10.0.16237.1001]
(c) 2017 Microsoft Corporation. All rights reserved.

C:\>dir
 Volume in drive C has no label.
 Volume Serial Number is 7216-718A

 Directory of C:\

07/03/2017  03:14 PM             1,894 License.txt
07/02/2017  03:39 PM    <DIR>          PerfLogs
07/03/2017  03:15 PM    <DIR>          Program Files
07/02/2017  03:39 PM    <DIR>          Program Files (x86)
08/14/2017  08:15 AM    <DIR>          temp
07/03/2017  03:16 PM    <DIR>          Users
07/03/2017  03:14 PM    <DIR>          Windows
               1 File(s)          1,894 bytes
               6 Dir(s)  21,206,704,128 bytes free

C:\>cd temp

C:\temp>dir
 Volume in drive C has no label.
 Volume Serial Number is 7216-718A

 Directory of C:\temp

08/14/2017  07:55 AM    <DIR>          .
08/14/2017  07:55 AM    <DIR>          ..
08/14/2017  07:55 AM                36 test.txt
               1 File(s)             36 bytes
               2 Dir(s)  50,829,029,376 bytes free

C:\temp>type test.txt
The system cannot find the path specified.     <-- !! Doesn't work !!!!!!!!!!

C:\temp>type .\test.txt
The system cannot find the path specified.

C:\temp>type C:\temp\test.txt     <- !! Works only with the full path !!
This is a test!

C:\temp>copy test.txt C:\test.txt     <- !! Again, doesn't work without full path !!
The system cannot find the path specified.
 0 file(s) copied.

C:\temp>copy C:\temp\test.txt C:\test.txt
 1 file(s) copied.

C:\temp>cd ..

C:\>type test.txt     <-- !! Commands work fine when file isn't in a host mapped volume  !!
This is a test!

C:\>