https://github.com/jenkinsci/ldap-plugin/blob/e55d225ba2ef6c99ba9b3336fa4be9d8880be2c9/src/main/java/hudson/security/LDAPSecurityRealm.java#L1589 loops though something related to configs.
Did you report a bug? Did you upgrade the plugin? Did you restart jenkins? Did you look at th the listing bug list?