I used to work for a company that used NPR's well the truck where always beat POShits, and I was one of the guys that drove them like a sports car, well the floor of the box on one had been cracked for sometime to the point of having about a 3" rip in it that you could look down and see the road through, it got to the point when you drove around the box looked like a cowboy sitting on a saddle bumping and bouncing front to back and side to side, finally one day I was turning and one side of the box would raise up about 5" I thought it would be pretty funny if one day it just litterly fell off the truck, then I thought it might wreck me or flip the truck which I didn't think too much of, so I refused to drive the truck anymore they then retired it.
a funny side story was it was easy to accidentally leave the back door open, which most of the time another driver would point back and you would know to stop, anyways I was working by myself one day and I noticed someone doing the usual pointing back, so I figured at the next light I would pull over, so I went a little more then another driver came buy and was freaking out pointing back, so I pulled over, and it turns out this crack in the floor of the box had caught the end of an airmover cord and an air mover was dragging by the cord behind the truck, pretty funny we still laugh about it