Diplomat ADP 8322?

My dishwasher beeps and the start light flashes. If I press the start light til the beeps stop it sometimes goes on to finish the cycle, but some times it doesn't and just continues to beep, so we power it off and start again.
It doesn't display any error codes and I've checked and cleaned the filters. I think its the circuit board that controls the washing prgrammes.
Also, is the watar supposed to sit in the botton under the fine mesh filter?