Gary, the alkalinity of the never completely rinsed away detergent pulled oils out of the vinyl leading to its degradation which allowed water to get through to the steel underneath.
Steve, I have and still use the KDS58 I bought when they were introduced in 1977 and I have a builtin KDS18 also. I modified both of them to have the larger upper wash arm introduced with the 19 series. The lower rack of the 18s holds a lot more plates, saucers, etc because the space between the pins is not as large as in the newer models. I think it is two extra rows on the right side of the rack.
I recently acquired a 1989, used 3 times, Kenmore Ultra Wash convertible portable, a WP machine. It is like Jason once said, a hurricane in a box. It washes well in both racks no matter how much the items in the bottom rack block water from the lower wash arm from reaching the top rack because of the wash arm under the top rack. I like the water miser cycle with two washes and two rinses using 2.2 gallons of water for each fill and the cycle is relatively fast.
Marc, does your KA do the pulsing of the motor during the cycle? To get the full force of the water, the pump stops and then starts up several times with a full head of pressure. It cannot maintain this level of pressure with the pump running constantly because the sump does not hold enough water to supply the maximum amount of water to the pump unless circulation is stopped and then restarted. This pulsing modification was made sometime after the tall tubs were introduced so I don't know if your machine has it. Isn't it something to hear about cleaning problems with a KitchenAid when for so many years they washed and rinsed so well? Insanity took over after the 18 series.