Azure Service Bus Relay: MEX Endpoint Error 500

Hi,

I have exposed a Biztalk 2013 R2 Orchestration via a WCF service using the Biztalk WCF Service Publishing Wizard with a Sevice Bus endpoint.

I can see that the IIS WCF Application has established the relay links via the Azure management portal and I can invoke the RelayEndpoint however the MexEndpoint is always returning error 500 when trying to add a Service Reference in Visual Studio:

<Error><Code>500</Code><Detail>TrackingId:3624fb4d-5c92-4f9a-b9d3-6c1b85fb960d_G50, Timestamp:3/23/2016 12:29:25 PM</Detail></Error>

Metadata contains a reference that cannot be resolved: 'http://<servicepoint_URL>_Orchestrations.svc?xsd=xsd2'.

Any ideas, what could be causing this?

Regards,
Colin.