[Samba] Users can't access files on shares

[Luka Goltnik]

Hello fellow Samba experts,

I come to you in hour of need. :-)

I have successfully set up Samba 4. It's acting as a AD domain controller
and on it I have 4 users, 4 groups and 6 shares. For most of the time
everything works fine, but samba has occasional glitches.

The glitches appear in such way that one user is let's say editing excel
file, and after saving the file and exiting excel, another user wants to
edit it as well, but get's a window saying "Access denied. Contact your
administrator!".

So I go exploring what's wrong and open properties of that file, check the
security tab and notice that surprisingly there is no Group or user name
written as having rights to access this file.
When I try to add group to the permission box I just get an error "Unable
to save permission changes on <filename.ext>. Access is denied."

Please, if anyone has any idea what's happening with my crazy Samba dancer,
any help would be greatly appreciated, as we've just switched servers from
an old server running some old Microsoft software to new one with Linux and
Samba 4.

Regards,
Luka