I've noticed something viewing my profile recently. Some of the emoticon notification messages have suddenly disappeared after being present for days or weeks. The like/laugh/thanks etc. emoticon still shows on the individual post it was attached to, but the messages informing me (and others) of the notations have gone AWOL. I've come across at least three so far since I noticed it and they didn't all happen at the same time, although two were from the same post and happened close to each other (as far as I can tell).
Not a big deal to me personally, but I thought it might indicate a larger software issue you may want to look into.
Thanks.