Years ago I worked on an HP3000 mini computer. Just occasionally, always late on a Friday afternoon, doing a long compilation, the compilation would stop with a long strange error report. It wasn't a compiler error, it wasn't an operating system error, it wasn't in any manual, it didn't identify itself clearly, but it wasn't gibberish, it wasn't repeatable.
I always thought the HP3000 had been at it all week, it was close to home time on Friday afternoon, it was looking forward to the weekend, and its mind wasn't really on it.