Yes, they do and they are. Referring to the image you posted, when I pull the handle up the cams end up oriented facing from the outer sides of the hook, releasing the handle allows to springs to move the cams back towards their resting position and lock against the rack tubing. If you're saying that in that position the bag shouldn't move at all, even when applying some force to the side of the bag, then maybe the springs aren't applying enough force to the cams to lock the bag in place?

I might take this up with Arkel directly, just in case my Bug is faulty, though I'm pretty sure it isn't. There's no problem mounting it on the rack, just that it moves forward with the bungee hook attached.

Thanks for your ongoing help and patience.