Diplomat ADP8242 eternal wash mode

Inherited this rebadged SMEG when I bought the house. Current fault: filled OK on ECO cycle and then ran and ran and ran (as long as you like to leave it – current record: overnight) without heating the water. Worked OK on intensive wash though, but only for two weeks. Now does the same on that program. Any ideas to try before I buy a new board or throw the thing away? This is the third fault on this heap of junk in the space of a year.