This happens to me a lot. Though I believe I should discuss about this topic.
As you can see here, I have 3 notifications, but in truth I do not have any on the website. They notifications will bug and stay on the icon while I have already clicked on them. This happens a lot for me so I do not know if any others experience the same issue as me.
These are my most recent messages and notifications. I already have them read. If I were to not have them read they would be highlighted. I have gone through every message I have. I believe this should be fixed because whenever I look back into my DevForum tab, I always believe I have gotten notified.