I have this annoying thing...
Posts from around August '15 to July '16 are excluded from searching option (there are no results).
I noticed it with the "Find latest posts" option in profile. And it's also why I couldn't find some certain posts, when I was looking for them.
I'm not sure if it's only me with this problem (account settings somewhere?), or is this browser/cookie thing (but I did search with my phone, the results are the same).