To add entries to OpenLDAP directory, two command line utilities distributed with openldap can be used -
Even with the similar names, their workings are very different.
ldapadd connects to a running instance of ldap directory and adds the specified ldif as a normal client.
slapadd modifies directly the underlying files that slapd daemon uses. So, it should not be run when slapd server is running (and generally should only be used to initiate a new database).
Make sure your scripts are using the proper utilities in proper situation.