samba - Dec 2013 - User cannot write to own directory on samba 3.6.3

Hello,

I have Samba 3.6.3 installed on an Ubuntu 12.04 fileserver which uses a Samba 4
Active Directory server for user authentication. Here is the smb.conf:
http://sources.xes-inc.com/downloads/smb.conf.txt

Occasionally, a user accessing a share from a Windows 7 Pro client will become
unable to write to a file that they own in a directory that they own or that
they have write access through their group membership (rwxrwxr--). I have found
that this can sometimes be resolved by killing the smbd process for that
particular share on that machine (pid found via smbstatus). Connecting to the
share via a CIFS server or directly on the fileserver itself as that user allows
the user to write to the directory as expected, so this appears to be an issue
with Windows 7 interacting with samba.

Here's an example of a smbd log from a machine where the user could not
write to the directory or file, even after I killed the smbd process and
verified that there were no open file handles to this file:
http://sources.xes-inc.com/downloads/user.log.txt

What else can I try to debug this and prevent this permission problem from
occurring?

Thanks,

Andrew