I've seen this happening several times:
- I downvote an answer (and thereby my reputation decreases by one point);
- I reach the daily reputation limit;
- the answer that I downvoted gets deleted (or I cancel my downvote);
- then my reputations increases by one point (it shouldn't; this is not one of the exceptions mentioned here);
- many hours later, my reputation decreases by one point, but my list of recent achievements doesn't mention that.
So, in the end my reputation is what it should be and therefore this is not a serious issue. But it still looks like a bug: I simply should not get that extra reputation point.