In a lot of cases we find that wash-ability issues our customers are experiencing with their dishwashers is not a defect in the dishwasher but what is being introduced into the appliance.
Number one issue that I we see is: Too Much detergent or the use of those the little dishwasher pods.(Too Much Detergent)
We would only recommend detergent pods in washing machines but never in dishwashers.
The second issue we see is: Hard Water, if you have hard water you may need a water softener or an additive in your dishwasher to help soften the water to achieve good results.
Number three issue that we see is: Water going to your dishwasher is not hot enough to clean your dishes properly. You may need to raise the water temperature on your water heater or use the water heating option on your dishwasher to achieve good results.