sorry not familiar with the Cordova runtime and possible stupid, but can this create an override when there are multiple background notifications received and  still e.g the first one hasn't yet finished processing (to call  push.setContentAvailable(push.FetchResult.NewData)

besides that, as you already comment, it is important to state in the docs that the ' push.setContentAvailable(push.FetchResult.NewData)' should be called.