[Samba] Samba 4.4.8 AD member ads / nss fails to find group id

[Thomas, David]

I have a Centos 7.6 server with samba 4.8.3  configured as a member of 
an AD domain using "ads' security and the "nss" idmap backend.

Clients are unable to access the shares on the server - they repeatedly 
get asked for their credentials.

The smbd log shows the user authenticating and a mapping from the user's 
SID to their unix uid is found. However, it seems that access is denied 
after samba attempts and faile to find a mapping from the Domain Users 
group SID to a gid.

This all works on another server running samba 4.4.4.

smb.conf:

[global]
     workgroup = TESTDOM
     netbios name = member
     realm = TESTDOM.COM
     security = ads
     username map = /etc/samba/users.map
     idmap config TESTDOM: backend = nss
     idmap config TESTDOM: range = 1000-99999
     idmap config * : backend = tdb
     idmap config * : range = 100000-200000
     winbind use default domain = Yes
     hosts allow = ALL

     log level = 99

[projects]
     comment = Projects
     path = /projects
     read only = no
     create mask = 0775
     directory mask = 0775
     force group = defgrp


Log:

sid S-1-5-21-11111111-222222222-333333333-1262 -> uid 1093
[2019/03/28 10:24:24.088770, 10, pid=31159, effective(0, 0), real(0, 0), 
class=tdb] ../source3/lib/gencache.c:301(gencache_set_data_blob)
   Adding cache entry with 
key=[IDMAP/SID2XID/S-1-5-21-11111111-222222222-333333333-513] and 
timeout=[Wed Dec 31 19:00:00 1969 EST] (-1553783064 seconds in the past)
[2019/03/28 10:24:24.098383, 10, pid=31159, effective(0, 0), real(0, 0)] 
../source3/passdb/lookup_sid.c:1550(sid_to_gid)
   winbind failed to find a gid for sid 
S-1-5-21-11111111-222222222-333333333-513
[2019/03/28 10:24:24.098420,  4, pid=31159, effective(0, 0), real(0, 0)] 
../source3/smbd/sec_ctx.c:216(push_sec_ctx)
   push_sec_ctx(0, 0) : sec_ctx_stack_ndx = 1
[2019/03/28 10:24:24.098443,  4, pid=31159, effective(0, 0), real(0, 0)] 
../source3/smbd/uid.c:491(push_conn_ctx)
   push_conn_ctx(0) : conn_ctx_stack_ndx = 0
[2019/03/28 10:24:24.098465,  4, pid=31159, effective(0, 0), real(0, 0)] 
../source3/smbd/sec_ctx.c:320(set_sec_ctx_internal)
   setting sec ctx (0, 0) - sec_ctx_stack_ndx = 1
[2019/03/28 10:24:24.098487,  5, pid=31159, effective(0, 0), real(0, 0)] 
../libcli/security/security_token.c:53(security_token_debug)
   Security token: (NULL)
[2019/03/28 10:24:24.098508,  5, pid=31159, effective(0, 0), real(0, 0)] 
../source3/auth/token_util.c:810(debug_unix_user_token)
   UNIX token of user 0
   Primary group is 0 and contains 0 supplementary groups
[2019/03/28 10:24:24.098549,  4, pid=31159, effective(0, 0), real(0, 0)] 
../source3/smbd/sec_ctx.c:438(pop_sec_ctx)
   pop_sec_ctx (0, 0) - sec_ctx_stack_ndx = 0
[2019/03/28 10:24:24.098576, 10, pid=31159, effective(0, 0), real(0, 0)] 
../source3/passdb/lookup_sid.c:1209(legacy_sid_to_unixid)
   LEGACY: mapping failed for sid S-1-5-21-11111111-222222222-333333333-513
[2019/03/28 10:24:24.098600,  1, pid=31159, effective(0, 0), real(0, 0)] 
../source3/auth/token_util.c:1024(create_token_from_sid)
   sid_to_gid(S-1-5-21-11111111-222222222-333333333-513) failed
[2019/03/28 10:24:24.098625, 10, pid=31159, effective(0, 0), real(0, 0)] 
../source3/auth/auth_ntlmssp.c:83(auth3_generate_session_info)
   create_local_token failed: NT_STATUS_NO_SUCH_USER*

*I have also tried the following settings in the global section (copied 
from the working server), but get the same result:*
*
     winbind enum users = yes
     winbind enum groups = yes
     use sendfile = Yes
     guest ok = no
     dos filetime resolution = yes
     nt acl support = no
     directory mask = 0775
     follow symlinks = yes
     wide links = yes
     unix extensions = no
     log level = 99
     lanman auth = no
     lm announce = no
     min protocol = NT1
     host msdfs = no

Am I missing something?
**
Thanks,
David