Bug #11962 shows a similar symptom as to what I am experiencing. We have samba joined to AD domain. On using, wbinfo -P / -t there is a lot of delay in getting back the response. What i see is the following in the logs:

log.winbind-idmap:

[2019/11/11 08:37:33.923455,  1] ../lib/tdb_wrap/tdb_wrap.c:64(tdb_wrap_log)
  tdb(/var/lock/samba/mutex.tdb): tdb_lock failed on list 117 ltype=1 (Interrupted system call)
[2019/11/11 08:37:33.923522,  0] ../source3/lib/util_tdb.c:497(tdb_chainlock_with_timeout_internal)
  tdb_chainlock_with_timeout_internal: alarm (40) timed out for key HOHOPUADC103.hosting.XYZ.com in tdb /var/lock/samba/mutex.tdb
[2019/11/11 08:37:33.923536,  1] ../source3/lib/server_mutex.c:97(grab_named_mutex)
  Could not get the lock for HOHOPUADC103.hosting.XYZ.com
[2019/11/11 08:37:33.923579,  0] ../source3/winbindd/winbindd_cm.c:1022(cm_prepare_connection)
  cm_prepare_connection: mutex grab failed for HOHOPUADC103.hosting.XYZ.com
[2019/11/11 08:37:33.923590,  1] ../source3/winbindd/winbindd_cm.c:1253(cm_prepare_connection)
  Failed to prepare SMB connection to HOHOPUADC103.hosting.XYZ.com: NT_STATUS_POSSIBLE_DEADLOCK

log.wb-DOMAIN:
[2019/11/12 05:48:03.033654,  1] ../lib/tdb_wrap/tdb_wrap.c:64(tdb_wrap_log)
  tdb(/var/lock/samba/mutex.tdb): tdb_lock failed on list 118 ltype=1 (Interrupted system call)
[2019/11/12 05:48:03.033713,  0] ../source3/lib/util_tdb.c:497(tdb_chainlock_with_timeout_internal)
  tdb_chainlock_with_timeout_internal: alarm (40) timed out for key HOHOPUADC100.hosting.XYZ.com in tdb /var/lock/samba/mutex.tdb
[2019/11/12 05:48:03.033729,  1] ../source3/lib/server_mutex.c:97(grab_named_mutex)
  Could not get the lock for HOHOPUADC100.hosting.XYZ.com
[2019/11/12 05:48:03.033799,  0] ../source3/winbindd/winbindd_cm.c:1022(cm_prepare_connection)
  cm_prepare_connection: mutex grab failed for HOHOPUADC100.hosting.XYZ.com
[2019/11/12 05:48:03.033813,  1] ../source3/winbindd/winbindd_cm.c:1253(cm_prepare_connection)
  Failed to prepare SMB connection to HOHOPUADC100.hosting.XYZ.com: NT_STATUS_POSSIBLE_DEADLOCK
[2019/11/12 05:48:03.033914,  4] ../source3/libsmb/namequery_dc.c:77(ads_dc_name)

Use case for using samba and winbind as a client here is just to authenticate against AD.

Below is the smb.conf file:
mhstpuanb210-A:/# cat /nvp/config/current/group/smb.conf        
[global]
    workgroup = hosting
    realm = hosting.XYZ.com
    password server = 10.231.193.36,149.122.43.20,149.122.43.68,149.122.37.31,149.122.43.21,149.122.37.32,149.122.33.69,149.122.37.20
    netbios name = mhstpuanb210
    security = ads
    idmap config * : backend = tdb
    idmap config * : range =  75000-33554431
    winbind normalize names = no
    machine password timeout = 0
    template shell = /bin/clish
    state directory = /var/lib/samba/state
    cache directory = /var/lib/samba/cache
    private dir = /var/lib/samba/private
    template homedir = /var/chroot/home/%U
    winbind use default domain = true
    winbind offline logon = true
    winbind cache time = 120
    winbind refresh tickets = true
    winbind rpc only = yes
    allow trusted domains = yes
    server string = Samba Server Version %v
    log file = /var/log/samba/log.%m
    max log size = 2000
    passdb backend = tdbsam
    log level = 4
    min protocol = SMB2
[homes]
    comment = Home Directories
    browseable = no
    writable = yes

krb5.conf is automatically generated by samba in the /var/lock/samba/smb_krb5/ path:
[libdefaults]
	default_realm = HOSTING.ACCENTURE.COM
	default_etypes = aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96 arcfour-hmac-md5 des-cbc-crc des-cbc-md5
	dns_lookup_realm = false

[realms]
	HOSTING.ACCENTURE.COM = {
		kdc = 149.122.43.20
		kdc = 149.122.43.68
		kdc = 149.122.43.21
	}

I am unable to figure out the reason why this is happening and it is failing logins / getpwnam_r system calls that are routed through nss as well.