Actually this is THE MOST COMMON service complaint from customers on about any KA DW from the 15s-the 22 series.

KA DWs while very good machines overall were a little bit overly complicated and were much more often plagued by things going wrong that impacted their ability to clean well.

Most Common Problems,

1 clogged wash filter,

2 detergent dispensers that do not open [ often because of clogged wash filter or bad inlet valve, bad wash arm support or item stuck in drain valve ]

3 Bad inlet valve which allows insufficient water flow [ almost NEVER a clogged inlet screen ]

4 broken wash arm support and worn lower wash arm.

5 Item caught in drain valve holding it open or blocking a full drain, on 15-20 models

6 Bad Drain check valve on  21 and 22 models [ CV does not seal any longer which allows pump to pull air back into DW when washing and rinsing which greatly reduces water pressure especially in top rack ]

7 Bad-broken drain impeller in 15-20 machines that causes poor drain.

8 Hole in rubber tube going to top wash arm in 18-22 models, and feed spout for upper wash arm feed out of place or missing altogether.

There are also a large host of problems related to detergent usage and water temperature and condition that will affect ANY DW ability to do a decent cleaning job.

Water temperature is the first thing I'd check.  It should be at 120 degrees or higher, and you should run the tap to get it up to that temperature before starting the dishwasher.

My sister got rid of a perfectly good KDS-18 because she said it didn't get anything clean and even spewed black particles onto the contents.  It was simply a case of her not using the machine enough (like almost never -- she's single) and that it needed a good cleaning and de-crusting from sitting unused so much of the time.  With her being 350 miles away, I wasn't able to do the work for her myself and save her the expense of a new dishwasher.