Help me fix my Smeg DWI 612C dishwasher?

Can anyone please help....
The dishwasher turns on as expected and starts on all programs. The first part of the program runs the drain pump to empty the dishwasher, this is all fine but then it tries to move to the second part of the cycle which i think is to fill. This is where it all goes wrong !!! The machine sounds as if a pump starts for a second then the door bleeps and the pumping stops. This then just continues until you turn it off. This fault started a while ago and has been getting worse. Previously i could turn it off and back on again and it would clear the problem. I have taken it apart today and checked all the obvious for blockages etc but everything looks fine. Can anyone please help