Dishwasher drainage intermittent fault?

Miele Dishwasher model G863CVI
I have a fault with the appliance in that it will not always pass away all of the water after completion of a wash.
I have have tried just operating it with just a hot water cleaning wash and it has completed the cycle and leaves no water residue. Then the next time it is used on a normal application a residue of water is left in the bottom of the appliance. I always make sure that the items for cleaning are fairly clean before loading up. I have cleaned the filter(s) and removed the non return valve which I have also cleaned.
When the fault occurs the appliance does not indicate a malfunction has occured and the the washed items are all clean.