Is this happening for desktop, mobile or email notifications (or all of the above)? Also, is this happening with *all* notifications or just certain types? Let us know and we'll do our best to help.
Check your bell settings for that channel and see if you've opted-in to receive all notifications? You may be on the default setting, which is to receive notifications occasionally. Here's a guide to help check that plus your app and device level settings: https://goo.gl/giVA8o