samba - Jun 2015 - log file variable %U and %m strange behavior

Hello,

    I currently have 'log file' in smb,conf set to

log file = /usr/local/samba/var/%U.%m.log

My understanding is this would create a log such as
'username.machinename.log. What I'm getting in some cases is
'machinename.machinename.log. I will also get 'username.IP.log. Why the
discrepancy? Thanks.

Samba 4.2.1(Ubuntu 12.04 LTS)

smb.conf

# Global parameters
[global]
        workgroup = SAMBA
        realm = SAMBA.LOCAL
        netbios name = DC1
        server role = active directory domain controller
        dns forwarder = 75.75.75.75
        idmap_ldb:use rfc2307 = Yes

        #Debug Logging Information
        log file = /usr/local/samba/var/%U.%m.log
        log level = 3
        max log size = 524280
        debug timestamp = yes
        syslog = 3
        debug uid = Yes
        debug pid = Yes

        # Don't allow any updates | allow unsigned updates | only allow
signed updates (False | nonsecure | signed)
        allow dns updates = signed

        #Disable CUPS Printing
        load printers = No
        printcap name = /dev/null
        disable spoolss = Yes

        # Allow Opportunistic locks
        kernel oplocks = yes

        # Allow SMB2 Leases
        smb2 leases = yes

        # Add and Update TLS Key
        tls enabled = yes
        tls keyfile = tls/sambaKey.pem
        tls certfile = tls/sambaCert.pem
        tls cafile         #tls crlfile         #tls dh parms file 
[netlogon]
        path = /usr/local/samba/var/locks/sysvol/cimg.local/scripts
        read only = No

[sysvol]
        path = /usr/local/samba/var/locks/sysvol
        read only = No






-- 
-James