ADP8322 Dishwasher Problem

The customer says that this machine, when put on any programme, sometimes “near the end at the drying bit”, starts continually beeping and the pre-rinse light lights up instead of its programme light. I checked everything but could not find any faults, i even sat for 30 mins while it completed quick wash and came to the end as it should with a couple of bleeps and only quick wash light on. She said that the fault normally accurs on the quick wash too. I know this machine shows fault code via tha start button light but this isnt showing any fault. Its one of those ones where the customers explenation is a bit vague and you cant work out whether the faults with the machine, them, or you. Any ideas anyone?

Thanks

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