VLAN Tag changing on just one clustered control domain?

Got two control domains running on physical servers each running a number of ldoms. These two servers are clustered together.

On both servers, control domain, we have VSW set up with VLANS:-

VSW

    NAME             MAC               NET-DEV   ID   DEVICE     LINKPROP   DEFAULT-VLAN-ID PVID VID                  MTU   MODE   INTER-VNET-LINK

    vsw0             00:14:4f:fa:7e:1d net0      0    switch@0   phys-state 1               1                         1500         on

    vsw3             00:14:4f:fa:de:f8 net20     3    switch@3   phys-state 1               1                         1500         on

    vsw1             00:14:4f:fa:bf:71 aggr0     1    switch@1   phys-state 1               1    4,9,10               1500         on

    vsw5             00:14:4f:f8:06:79 aggr1     5    switch@5   phys-state 1               1                         1500         on

Each ldom is then configured with VNETS e.g.

NETWORK

    NAME             SERVICE                     ID   DEVICE     MAC               MODE   PVID VID                  MTU   MAXBW      LINKPROP

    vnet0            vsw0@primary                0    network@0  00:14:4f:fc:40:52        1                         1500             phys-state