Every once in a while, when the columns are somewhat narrow. The text justifier doesn't do it's job:
If I force it into a fixed number of columns, I can make it fail spectacularly by making the columns very narrow. However, using Auto columns, I still get the problem above where it fails from time to time.
Wiki Links: Enabling Logging / Detailed Search Help - MacBook Pro (2014), ThinkPad E570
This is by design. In cases where the justification gaps would get too big (either there aren't enough words on the line, or the line ends well before the justified width), we just leave the line unjustified.