New Webhooks feature timing out for all requests. (BB-13419)

Hi,

I've registered a simple new webhook (just a Runscope capture, so I can view the content of the posts), but every hook is timing out:

All the Runscope endpoint does is log the request and respond with a simple 200 response with some JSON debugging info in it. It worked for the old "Pull Request POST" service.

Am I doing something wrong here? Is there a specific response that the new webhooks require? Or is this a genuine bug with the new service?