Another success story here: Sears Kenmore Ultra Wash III, leaking intermittently from beneath the front door and/or beneath bottom panel.
After following MANY false leads (checked float, cleaned gasket, cleaned spray arm, checked torx screws below spray arm), and thinking we'd got it once or twice (the intermittent leaking stopped temporarily), removing the decorative front panels finally made it clear that the leak was coming from somewhere in the neighborhood of the push buttons near the vent. Cardboard spacers were absorbing the water and making the leak intermittent--but the pattern of water damage to the cardboard made the path of the leak pretty clear, and the origin of the leak was also apparent when running the dishwasher with the spacers as well as the front panels removed.
On removing the vent cover (it just pulls off), I found that the vent was throughly clogged -- mostly with paper fibers from labels of glass jars that had been washed (against manufacturer's advice!).
Cleared the vent and all is well.