I mentioned this previously, offhandedly, in another thread but as I am seeing this condition persist and become more frequent, I thought to maybe start a thread on it to help raise awareness and possibly get it fixed.
To restate, I am noticing that not all notifications are displaying, or even notifying me through the notifications alert system. I have reactions set to be marked by notification and yet a reaction that was just issued does not show up there. However, if I go to my profile, I can see that the reaction was registered there within the Activity tab. The missing reactions in question were issued and never logged by the Notifications function so it shouldn't be a cache issue.