NPIV has not been changed since initial install, always had NPIV enabled, which I believe is the default.
Double checked port and partner port in same switch.
We just changed to patch P103 last night actually and then tried node reboot after, so latest patch not fixed, but thanks for suggestion.
This from pre-upgrade looks promising though: -
"Brocade FOS 7 switches have a "F-Port login parameter" named "Enforce FLOGI/FDISC login" set to 0. Which means it will NOT allow a duplicate pWWN to be advertised on multiple ports. And due to that it has a tendency to break the 3PAR persistent port feature at times since at failover or failback time it is not possible to get the pWWN moved. When this is determined by the switch it will place the target port into a persistent disabled state."
I do remember reading this and I think I dismissed it because it said Brocade FOS 7 and we have OS v8.
I've checked the setting and it is configured to 0, which can cause this problem, so looks like we need to change to 2 to fix.
Probably won't be until next week now until I get to do that, so will update post with results then.
Thanks for help and suggestions guys