We use Remote Role Groups, the question is not related to local users authentication.
Debug Trace if login fails:
nslcd: DEBUG: accept() failed (ignored): Resource temporarily unavailable
nslcd: [8b4567] DEBUG: connection from pid=30353 uid=48 gid=48
nslcd: [8b4567] <authc="adm_user"> DEBUG: nslcd_pam_authc("adm_user","httpd","***")
nslcd: [8b4567] <authc="adm_user"> DEBUG: myldap_search(base="DC=company,DC=int", filter="(&(sAMAccountName=*)(sAMAccountName=adm_user))")
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_initialize(ldaps://ldap.company.int:636)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_rebind_proc()
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_PROTOCOL_VERSION,3)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_DEREF,0)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_TIMELIMIT,30)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_TIMEOUT,30)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_NETWORK_TIMEOUT,30)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_REFERRALS,LDAP_OPT_ON)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_RESTART,LDAP_OPT_ON)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_X_TLS,LDAP_OPT_X_TLS_HARD)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_simple_bind_s("CN=ldap,OU=Orga_User,OU=Benutzer,OU=company,DC=company,DC=int","***") (uri="ldaps://ldap.company.int:636")
nslcd: [8b4567] <authc="adm_user"> DEBUG: set_socket_timeout(30,500000)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_result(): CN=XXXXX\, YYYYYY (ADM),OU=Benutzer,OU=ADM,DC=company,DC=int
nslcd: [8b4567] <authc="adm_user"> DEBUG: myldap_search(base="CN=XXXXX\, YYYYYY (ADM),OU=Benutzer,OU=ADM,DC=company,DC=int", filter="(objectClass=*)")
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_initialize(ldaps://ldap.company.int:636)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_rebind_proc()
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_PROTOCOL_VERSION,3)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_DEREF,0)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_TIMELIMIT,30)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_TIMEOUT,30)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_NETWORK_TIMEOUT,30)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_REFERRALS,LDAP_OPT_ON)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_RESTART,LDAP_OPT_ON)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_set_option(LDAP_OPT_X_TLS,LDAP_OPT_X_TLS_HARD)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_simple_bind_s("CN=XXXXX\, YYYYYY (ADM),OU=Benutzer,OU=ADM,DC=company,DC=int","***") (uri="ldaps://ldap.company.int:636")
nslcd: [8b4567] <authc="adm_user"> DEBUG: set_socket_timeout(30,500000)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_result(): CN=XXXXX\, YYYYYY (ADM),OU=Benutzer,OU=ADM,DC=company,DC=int
nslcd: [8b4567] <authc="adm_user"> DEBUG: set_socket_timeout(15,0)
nslcd: [8b4567] <authc="adm_user"> DEBUG: ldap_unbind()
nslcd: [8b4567] <authc="adm_user"> DEBUG: bind successful
nslcd: [8b4567] <authc="adm_user"> DEBUG: myldap_search(base="DC=company,DC=int", filter="(&(objectClass=shadowAccount)(uid=adm_user))")