I'll attach the project to this discussion .. but first question is should a client be able to create multiple subscribers (each subscribing to a different subject)?
If so I'm assuming there is some kind of defect, since when I publish to the second subject the test app fails to make UI updates.
.. when I change to the code below everything works fine (the images on the app start to randomly change)
Yes, of course clients can subscribe to multiple subjects. I have just tested your app to confirm the client-side message callback is invoked for both subjects ("status" and "status2"). Are you sure your callback is not invoked and it's not a UI problem?
Do you see errors in your browser's JS console or in Dev Mode?