[Samba] NT_STATUS_ACCESS_DENIED: Access denied (0xc0000022)

[Mark Foley]

I have a Samba4 AD/DC running on Slackware64 14.1, Samba version 4.2.12. This computer has been
serving a Domain of several Windows 7 and one Linux domain members for about 2 years without problem.

On a few occasions lately I've run the following command on the AD/DC:

$ ntlm_auth --username="user" --password='password'
NT_STATUS_ACCESS_DENIED: Access denied (0xc0000022)

and have gotten the access denied message shown.  In other words, domain users suddenly can't
authenticate.  Stopping and restarting samba does not fix the problem.  The samba log has:

[2016/09/02 11:19:36.490991,  2] ../libcli/auth/credentials.c:403(netlogon_creds_server_check_internal) credentials check failed
  
I have to reboot the computer to fix this.

It looks like my last update to Samba to 4.2.12 was done on July 2, 2016.  It's probable that I
started noticing this problem about then.  It is very intermittant.  Probably less than 8
times since then. 

Can anyone tell me why this is happening and how I can fix it without having to reboot?

This is important as this is a production machine and users are unable to log into the domain
when this happens. 

THX -- Mark