Since fanfiction.net does not have native support for downloading fanfiction, I've been using a third-party program to do that for around a year now.
Recently I've been going through all my saved fics to implement a new sorting system that makes it easier to see whether I need to check for updates (as well as actually checking for updates) before making a new set of backup copies. This means opening up every single fic I have downloaded in order to get to the version published online.
While doing this, I notice that for some reason a few of the saved one-shot fics are missing the only chapter they have. They have all the identifying information and the chapter title present, but there's no actual fic.
This calls for a investigation!
After some research, I discover some important things about this problem, namely that A). this is a randomly occurring issue with the downloader that was introduced in the previous version, B). the bug has no discernible cause or fix, and C). there's been no word from the person developing the downloader in years.
So now I'm currently going back through all the ff.net fics (including the ones I already sorted) checking for missing chapters, and re-downloading them (sometimes multiple times) until all chapters are accounted for.