As you can see on the reputation tab on my profile, I received some up-/downvotes on my most recent post:
However, I did not get any notifications about them (the upvotes), nor do they even appear in the achievements dropdown (both up- and downvotes):
They started to show up one by one (with a bit of a delay between each one).
The last one is still not shown. Is this some kind of a caching issue?