Dishwasher not draining fully

I don’t know this appliance and I don’t know if have a pomp for drainage or is only from gravity, the main drainage need a check and clean if is necessary, check the hight of the loop for water to flow out and have a fall

Check the position of the drain hose connected to your dishwasher. It should be a minimum of 50cm and a maximum of 100cm above the floor to work correctly. Remove the filters from the base of the appliance and check if they are blocked. If they are, rinse them under a tap to clean, and then replace them.

would ask the customer if there is any flashing lights if so what colours are flashing and are they flashing at a sequence.

If the customer answers yes to the above then I would search the manufacturers guide to what fault code the flashing sequence lights are. Normally certain colours or sequences relate to a fault code. Once matching the fault code to the manufacturers guide this will give a explanation what the fault issue is

You should clean the drainage first and after fit proper the dishwasher pipe