The Jandd Expedition is an excellent rack, and it seems unlikely it was a positioning issue -- there are two stops on the rails that would keep the Arkel retaining system secure:


However, the Jandd doesn't seem to have a secure place for the bottom hook, so I wonder if that could be a problem -- that the bottom hook slid off the bottom rail, removing tension from the retaining system. Other racks have a place for the hook, such as the Blackburn:


However, if the asymmetrical retaining clamp were rotated the "easy" way, I suppose it's possible it could rotate by itself and allow the hooks enough play to bounce up.




I hope you get to show it to the Arkel people; I'd be interested in what they say.

RichC