My app is behaving different on Android but works just fine on iOS.
So, when my app backend is sending multiple Push Notifications to a particular User/Device, only the last received message is retained in Status/Notification Bar in Android. It works as expected in iOS (i.e. I can see all the incoming push notifications in the Status/Notification area).
It works with no issues when the app is running and in the foreground.
I came across following and going to see if I can change the Notification ID of an outgoing push notifications. I thought of putting it here in case anybody has a different solution.