I have said this at least once before - I have seen chassis wear on this model more so than any other which came after the original five Turbopower models from 1983. Originally there was no washer behind the wheel, only in front. At some point around the time that the original models were discontinued, Hoover made a number of cost-cutting changes, including using 3 clips on the fan cowling instead of 4, and a new way of securing the front wheels to the cleaner.
In addition, a second washer was placed behind each of the rear wheels, to prevent them wearing into the chassis. This is a great example of managing "planned-obsolescence", because everything one buys has been designed to wear out or else the manufacturers would never sell anything new, yet if they get it wrong and parts wear out too quickly, it becomes problematic for all involved. In this instance, the Turbopower chassis were wearing out very quickly, so Hoover overcame this by simply adding the extra washers. It is more than fair to say the cleaner already contained enough weak-spots to allow it to eventually break-down, without the need for the chassis to fall apart too.
But for some reason, the green U2332 model will often be found without the extra washers, leading me to think that either someone who worked on that production line for a very long time was making a mistake by not fitting 2 washers to each wheel, or that a good deal of stock of the U2332 was manufactured long before any of the other colours. This was undoubtably Hoover's flagship model of the era - the one which probably cost the least to build (taking account of the fact that the Junior model had a lot more metal and similar assembly costs, and the autoflex had more parts and more assembly - the costs of all of this possibly never being reflected in the final selling price), and I know Hoover liked to keep plenty of stock, so I'd not be at all surprised if a good deal of them were built prior to the actual launch date.