Not really done much container work, so only aware of the straight frames… but that doesn’t sound like an ideal design - though I guess it’s like anything, perfectly suitable if you don’t go rallying it around corners.
Hadn’t noticed it before, but at the very end of the vid clip, you can see the scrapes on the ground where the container has came off pretty much right on the exit of the RA, so for it to go that far, and the unit / trailer to go so much further… im no physicist, but that must have been near enough flat-out 
toby1234abc:
TNUK CSI , hold on lads and lasses, have a look at the roof of that container , the cargo looks bulky and made a big dent .
With containers having bolt locks, the driver can’t check if the load is unstable or top heavy .
Which is why you’re supposed to drive them sensibly, right? 