Smeg DWI 612 Integrated Dishwasher

I’ve got E8 coming up at start after 30 secs to 5mins.No regular pattern but sometimes it fills AND circulates,then the familiar beep beep and abort.Fitted new board 816290713 and same fault! The handbook says E8 means no water pressure to spray arms but the circ pump works when the prog gets that far.Is there maybe a circ pump pressure switch intermittent?I havent yet pulled it out (loads of work)but its only 2 years old and done no work,clean as a whistle,I dont recon theres any crud around.I also tried the old trick of turning down the tap to slow down the fill which sometimes works.Run out of ideas now. Any clues gratefully received.
Cheers Bob.