Facebook not pushing certain notifications!

[xIntimidatorSSx]

Hello all! This is my first post on here. I have a Verizon Galaxy S4 (love it) and I have a question. Sometimes Facebook won't send push notifications. A lot of it seems to be with group posts too. I have every Facebook push notification on. If I have no notifications, open the app, hit refresh, then all of the sudden the notifications pop up but my phone never told me I had them. It just sucks sometimes having to open the app and hit refresh just to see if I have a notification from a group post I commented on. Is this a Facebook issue or a Samsung issue? Thanks in advance.