Hey there,
We’ve noticed that some v12 worlds take longer to start up in general. ECONNREFUSED happens when the time is longer than 30 seconds, but usually a subsequent attempt to connect will succeed. This simply means that the world has taken more than 30 seconds to start up, which is longer than expected, rather than something expressly having gone wrong.
We’re improving the feedback and extending the time allowed for the server to start up and become ready, which should remove the disruption that this error causes!