The LDAP connection is always successful. But, sporadically, while retrieving the second LDAP attribute specified in the Authtentication Service rule, getting NullPointerException with those errors in PegaRULES.log
I assume you are using replicated ldap environment to read the data from ldap. Across all the servers ldap schema might be different(may be one of the attribute which is failing to load is not defined in the schema). When the request is hitting the ldap through the load balancer some of them are giving the successful result and one of them is failing to serve the request due to inconsistent schema across the ldap environment. Please validate the schema in all the ldap servers and let me know if you find any differences.