I have no experience in dishwashers but a friend has a question.
After the wash programe has finished the items in the lower basket are only partialy clean and all items in both baskets are left with a gritty residue baked on. Have tried changing the salt and rinse aid levels and using a high programe.
Underfilling? Pressure chamber in the 3 o’clock position in the sump. Failing that a blockage in the pump inlet? Got a medicine spoon out of one recently, giving exactly the same symptoms.