Backup bike saddle had a bad habit of just suddenly coming loose whenever I *didn't * have a multi-tool on me. I thought it was finally fixed by last LBS in Lanesboro visit. Houston LBS showed me the problem was basically like a stripped screw. Which was why it sometimes worked--and sometimes didn't.
He replaced it and saddke, and new saddle has 2 bolts instead of just one, so that has made things much better.