[Samba] can't log in as domain admin

[Gary Dale]

I'm running Debian/Jessie (stable) on an AMD64 machine, with Samba 
Version 4.1.17-Debian. This is the domain controller, DNS server, Time 
server and File server for the local network.

The problem I'm having is that Windows machines sometimes can't open 
files for editing. Other files in the same directory don't have that 
problem.

When I look at the Unix permissions, the files causing problems have a 
windows user number as the owner while the ones that don't cause 
problems are owned by nobody. In both cases the Unix permissions are 
everyone has read-write-execute access to the files. Changing the Unix 
permission had no impact.

Where I hit the snag however was trying to change the ACLs so that 
Domain Users should have read/write/execute permissions. I can't log in 
with the domain administrator account on any of the Windows machines. I 
get an error message saying user name or password is incorrect.

I've used smb-tool on the DC to change the password so I know it is 
correct. And Domain Admins are in the local Administrators group on the 
Windows machines.

Any tips on tracking down the problem?