Newer notifications of the same thread-id seems to replace the older one, rather than visually grouped, causing older notifications to not be visible. I've always observed this, but never really check into why it happens.

May I ask if apns-collapse-id is set from the server end? Read some sources suggesting that might be why. Trying to know if this is a problem that I can resolve from client side or if it's a server side thing, thanks!