How can I fix my dishlex 106?

The dishwasher dial keeps sticking mid-cycle, resulting in the cycle never finishing. At one stage a few months ago, this caused the home safety switch to go off at the same point each time. When we reset the safety switch and moved the dial one click past the point where it stopped, it continued to wash. We didn't use it for 2 months and tried again last night; it didn't short out but the dial stopped at a point and the dishwasher didn't stop working, ie, it kept washing. I moved the dial one notch and it continued to wash then finish the cycle.