Since the latches were fixed it appears that slop between the upper mounts and the latch 'may' be causing some bags to fly off during bumps. It doesn't hurt to check this clearance every once in awhile. Grab the case and try to move it up and down with it latched to the bike. If there is substantial movement (sorry, can't tell you how much is bad) then you may be a candidate for this happening. I would think that more weight in the case would actually increase the force (Brian?) during a bump to the point where it may override the latch and become a depth charge (I have this mental image of that happening).
Additionally, you should check the lower case mount for tightness. It tends to work loose. You can either do nothing (like Steve and many others), pin it, or use Zsteve's bars (I'm in that category). Pinning is cheap insurance. Zsteve's bars really lock it tight to the bike and provide a little insurance against anyone removing them.
I also want to say that the riders here that have had that happen are seasoned and I doubt very seriously that the cases were installed incorrectly. If the rider had just got the bike and they flew off, I could see that happening.
