GSD2100V55WW was working just fine.

Now the water will come in, the arms will spin, I hear the pump running the spray, but the knob does not advance to the next step. After a period of time (15 mins.) I rotate the knob to the next click and the next process starts (ex. draining) and completes, (empty tub), but the machine does not advance to the next step (whatever). So it continues to drain, or whatever. I guess it doesn't overflow onto the floor because a safety cutoff stops the filling.

Not really old, but not new. Is there something I need to clean or observe?

A similar post on a different GE DW got a reply of replace bad timer, but I don't want to jump to conclusions.