Whirlpool DWF 416 More beeping

We have a 2-year-old Dishwasher (Whirlpool DWF 416) which seems to have a problem with the rinse cycle. In any setting, the machine works just fine for say 30-50 minutes (depending on the programme selected) after which it starts beeping incessantly. The machine then stops working, and the beeping continues. Upon opening the door, the dishes are clean but not rinsed, and the “start” button is flashing. We have checked the pipes, the filter assembly, the rinse aid and the salt container. (NB: We also have the problem of the beeping at the start of the programme which was recently described by another user, but this problem is solved as you described). We would be very grateful if you could suggest a solution for us. Thank you. Samia