Cross Host Fencing Problem with vCloud 5.1

Hi,

I have 6 ESX 5.1 hosts in my vCloud resource cluster, all works fine except that if I create a fenced vApp and the vShield Edge device or VM land on a certain host then I can't talk to the VM.  If both the Edge device and the VM land on the suspect host together it's fine.  All other hosts work OK.

I'm using VLAN 220 for the Network Pool so I thought that it may not be presented to the dodgy host but that is not the case.  I'm pulling my hair out over this one, can anyone assist me here?

thank you