Haven't had one 'leave the building' yet, but I have had them come loose and end up hanging out the side of the truck or bouncing around under the body. Also noticed one of my 2S packs split the hard case and the cells show a little squishing from whatever impact did the damage. No puffing though, and it still charges and holds voltage as well as it ever did. Time will tell if it is damaged as I plan to keep using it for now.
A buddy of mine I ran with last year had a v2 talion. His packs seemed to fly more often than the truck. Then again, he wasn't very diligent with his velcro... think he had one strap and it was half torn. Seemed stupid to me to have a $100 bill flying out of the truck so frequently when a $5 piece of velcro would stop the issue.