Integrated European units are where most companies give up. Miele and Bosch panels come off in a specific order, and the error codes actually mean something.

Standing water at the end of the cycle is usually the drain pump, the check valve or a blocked air gap at the sink. On a lot of houses the actual fault is the garbage disposal knockout plug that was never removed when the disposal was installed, which means the dishwasher has been draining through a wall this whole time.
White film on glassware in the Valley is nearly always water hardness rather than a broken machine. Hard water leaves scale on the heating element and the spray arms, the detergent stops dissolving properly, and everything comes out dull. That is a descaling job plus a rinse aid setting, not a parts replacement.

Yes. Those are the units most shops turn away, and they are a large share of what we do.
Usually the upper spray arm feed, either scaled shut or disconnected from the rack adjuster.