Firebase onDataChange() not working on some devices

Question

I have developed an app which receiving real time data change from Firebase node.

I am calling below example code for fetching data change if happens in Firebase table for particular node.

private class MyValueEventListener implements ValueEventListener {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Log.i("********** change", dataSnapshot.getKey() + ": " + dataSnapshot.getValue());
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // If we're not expecting an error, report it to your Firebase console
        FirebaseCrash.report(databaseError.toException());
    }
}

Issue: For example 400 devices are there which are in for my app then out of these 400, randomly 20-30 devices are there which are not getting callback in onDataChange method.

I am searching for this from so many days but not able to find the solution.

Any help would be deeply appreciated.