the machine is ok for about an hour then it stops on the rinses with what looks like the correct level of rinse water in the drum. I have checked the valves, water pressure and that the machine is not syphoning. When rinse and spin or spin is selected individually the machine works ok.
What was the sump and pressure switch modification to rectify?
Went to a very similar fault today on a WF series machine. However machine intermittently over filled. Pressure vessel was filled with smeg. You do not say if you checked pressure pot. If you have not, perhaps you should. good luck.