Going to use the kitchen sink as the example: If you modify KS so that it registers the background service each time you pause the app (by putting it in the pause eventlistener), the eventlistener on the notification defined in the bg service only works one time. If you background the app a couple times, you will see in the console that they don't work.
Similarly, if you schedule multiple notifications during one background service call, the event listener only works once. (occasionally not at all!).
To reproduce, just modify kitchensink to put the background service registration into the pause event listener.