Real time SSE: add a message

Can you provide guidance?

I don't have the shoelace error and duration is working for me. (at least was...).
But I have other problems with SSE which seems to not work on dev mode (twig dump on), as well when you drop a views (like block Who's online).
Even on a clean install it seems to not work anymore on 1.0.x, but I need to ensure it's not a local problem.