What switch are you using?
does video pass to the other endpoints that do not have matching firmware?
it's always been my experience with NVX to match all firmware (annoying but keeps everything working better).
A storm is most likely a bad registration or the switch not handling the registrations correctly.
What IGMP version is configured on the switch and the NVX's?
When the storm happens does it lock up everything?
What else is on the VLAN with the NVX's?
What processor and port are you using?
