Login to Big-IP 14.1.2.3 and 15.0.1 Configuration utility via LDAP fails with nearly 50% probability

Greetings,

After update from Big-IP 14.0.0.3 remote LDAP authentication fails time to time using the same correct credentials (i.e. 3 negative responses and following 2 are positive). I've tried to change idle timeout with no luck. ldapsearch responds with 0 Success code. Sometimes it takes 5 attemptes before I am logged in.

/var/log/secure:

Mar 5 13:30:13 mybigip.com err httpd[31489]: pam_ldap(httpd:auth): error reading from nslcd: Connection reset by peer
Mar 5 13:30:13 mybigip.com warning httpd[31489]: pam_unix(httpd:auth): check pass; user unknown
Mar 5 13:30:13 mybigip.com notice httpd[31489]: pam_unix(httpd:auth): authentication failure; logname= uid=48 euid=48 tty= ruser= rhost=192.168.5.10
Mar 5 13:30:16 mybigip.com err httpd[31489]: [auth_pam:error] [pid 31489] [client 192.168.5.10:53225] AUTHCACHE PAM: user 'f5' (fallback: false) - not authenticated: Authentication failure, referer: https://192.168.5.5/tmui/login.jsp
Mar 5 13:30:16 mybigip.com info httpd(pam_audit)[31489]: User=f5 tty=(unknown) host=192.168.5.10 failed to login after 1 attempts (start="Thu Mar 5 13:30:13 2020" end="Thu Mar 5 13:30:16 2020").
Mar 5 13:30:16 mybigip.com info httpd(pam_audit)[31489]: 01070417:6: AUDIT - user f5 - RAW: httpd(pam_audit): User=f5 tty=(unknown) host=192.168.5.10 failed to login after 1 attempts (start="Thu Mar 5 13:30:13 2020" end="Thu Mar 5 13:30:16 2020").

nslcd in debug mode:

nslcd: DEBUG: accept() failed (ignored): Resource temporarily unavailable
nslcd: [43a858] DEBUG: connection from pid=31489 uid=48 gid=48
nslcd: [43a858] <authc="f5"> DEBUG: nslcd_pam_authc("f5","httpd","***")
nslcd: [43a858] <authc="f5"> DEBUG: myldap_search(base="OU=admins,DC=mydomain,DC=com", filter="(&(sAMAccountName=*)(sAMAccountName=f5))")
nslcd: [43a858] <authc="f5"> DEBUG: ldap_result(): CN=f5,OU=admins,DC=mydomain,DC=com
nslcd: [43a858] <authc="f5"> DEBUG: myldap_search(base="CN=f5,OU=admins,DC=mydomain,DC=com", filter="(objectClass=*)")
nslcd: [43a858] <authc="f5"> DEBUG: ldap_initialize(ldap://mydomain.com:389)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_rebind_proc()
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_PROTOCOL_VERSION,3)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_DEREF,0)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_TIMELIMIT,30)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_TIMEOUT,30)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_NETWORK_TIMEOUT,30)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_REFERRALS,LDAP_OPT_ON)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_set_option(LDAP_OPT_RESTART,LDAP_OPT_ON)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_simple_bind_s("CN=f5,OU=admins,DC=mydomain,DC=com","***") (uri="ldap://mydomain.com:389")
nslcd: [43a858] <authc="f5"> DEBUG: set_socket_timeout(30,500000)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_result(): CN=f5,OU=admins,DC=mydomain,DC=com
nslcd: [43a858] <authc="f5"> DEBUG: set_socket_timeout(15,0)
nslcd: [43a858] <authc="f5"> DEBUG: ldap_unbind()
nslcd: [43a858] <authc="f5"> DEBUG: bind successful
nslcd: [43a858] <authc="f5"> DEBUG: myldap_search(base="OU=admins,DC=mydomain,DC=com", filter="(&(objectClass=shadowAccount)(uid=f5))")
nslcd: [43a858] <authc="f5"> DEBUG: ldap_result(): end of results (0 total)
nslcd: [1d5ae9] DEBUG: connection from pid=31489 uid=48 gid=48
nslcd: DEBUG: accept() failed (ignored): Resource temporarily unavailable
nslcd: [1d5ae9] <get_attributes="f5"> DEBUG: nslcd_pam_get_attributes("f5","httpd","","192.168.5.10","","***")
nslcd: [1d5ae9] <get_attributes="f5"> DEBUG: myldap_search(base="OU=admins,DC=mydomain,DC=com", filter="(&(sAMAccountName=*)(sAMAccountName=f5))")
nslcd: [1d5ae9] <get_attributes="f5"> ldap_search_ext() failed: Can't contact LDAP server: Connection reset by peer
nslcd: [1d5ae9] <get_attributes="f5"> DEBUG: set_socket_timeout(15,0)
nslcd: [1d5ae9] <get_attributes="f5"> DEBUG: ldap_unbind()
nslcd: [1d5ae9] <get_attributes="f5"> DEBUG: "f5": user not found: Can't contact LDAP server

/var/log/httpd/httpd_errors

Mar 5 13:13:34 mybigip.com err httpd[31490]: [auth_pam:error] [pid 31490] [client 192.168.5.10:52914] AUTHCACHE PAM: user 'f5' (fallback: false) - not authenticated: Authentication failure, referer: https://192.168.5.5/tmui/login.jsp?msgcode=1&

/var/log/daemon.log

Mar 5 13:13:33 mybigip.com warning nslcd[3968]: [a2a8d4] <authc="f5"> ldap_search_ext() failed: Can't contact LDAP server: Connection reset by peer

Thank you in advance for help=)