A 'shimmy' at high speeds

A woman ran over a mattress and decided to keep going.
The ensuing jumble finally whipped around enough to put a tear in the gas tank.
The subsequent lack of fuel is what finally brought this vehicle to its knees.
It had still managed to drive 30 more miles decently with a 60lb tangle wrapped around the driveshaft.
This genius complained that the vehicle had a "shimmy" when driving at high speeds.
This is what the dealership found . . .