Jan,
Thanks for your reply and the info.
Concerning the switching DADman to sync source from Dante, this had been tried with no change.
Your responses though made me rethink connectivity and I did discover an issue from the main Dante switch being used and a local hub switch.
The MTRX St, Mac Pro DADman port and the Thunderbolt to ethernet adaptor that the DVS is running through on the Mac Pro are now all on the local hub and passing audio. Reconnected to main switch and I now have the rest of the Dante network available.
There are other Latency Errors to work out on the rest of the rooms but this solved my initial issue.
Thanks for the input.