The Courts may find that the dishwasher is being used for a purpose it wasn't intended for. You should have bought an industrial dishwasher. Quality includes the appearance and finish of the product. You buy a new car, but discover the seat fabric doesn't match and the paint is chipped. Clearly this is unacceptable and constitutes a failure in appearance.
Quality includes freedom from minor defects .
We have again purchased a new car. The radio is faulty and the air conditioning works intermittently. These clearly do not effect the safety or driveability of the car and the car still looks good. But you've paid a lot of money and these things should work. Again the court will consider the extent of minor flaws and the work required to fix them.