So this is a big problem here in Aus, and not just with the Mitsi's, it's being seen on basically all the dual cab 4WD utes. The cause has caused quite a bit of contention too, with air bag helper springs being blamed by many. The thought was that the air bags are forming a pivot point on the chassis that it just wasn't designed for, add way too much weight on the back end, and presto. This car has no air bags gps fleet tracking
however, and they have nothing to do with it.
So, basically, way too much weight in the tray, plus towing close to (if not more than) maximum load, plus driving too fast over our fantastically **** roads, especially outback corrugations. Chassis just can't cope with the extreme amount of load being placed on the very back of it.
It's actually such a big problem in the outback that a lot of independent research has gone into finding the cause and a solution, and it basically boils down to operator error.