You must be having stale keys remaining in your disks. You may want to check the same using # vxfenadm -s /dev/sd*. Also you can clear them using # vxfenclearpre. Ensure fencing is not online on any node while clearing the keys.
As suggested by Gaurav , please attach the main.cf file. Also please note PrivNIC and MultiPrivNIC agent is not supported if your Oracle RAC is above 11202 since Oracle HAIP takes care of private ip failovers/failback.