After years of using Rockbox I've finally discovered why it sometimes very annoyingly switches to shuffling playback of my carefully ordered playlists and directories of mp3s.
Its the "Quickscreen" which defaults to having "shuffle", "repeat" and "show files" options.
So if I accidentally press my "home" key for too long, then press left, right, up, down, I get the incredibly annoying problem that the next file I play is the wrong one (the wrong chapter, when playing an audiobook is really bad!)
Now that I have found these settings I have changed them to things less problematic for accidental key presses; Volume and LCD brightness.
I'm going to do that for my wife's player next time I get hold of it, because its her that presses random keys the most, and then complains to me that her player plays chapters in the wrong order!
So here's my suggestion: Please change the default "Quickscreen" buttons to ones that are less frustrating: eg Volume and LCD brightness.