After a day on it, I just noticed this was only happening when debugging, when in production there is no problem anymore.

I suspect that due to some bugs later in the code, the script was exiting before publishing on the MQTT, although I am curious as to why a breakpoint did not make the eventBus publish?

A good tip in such a situation is to place a good old setTimeout for 2 second to check if it is the cause.

Hope that helps if other people have the same issue.