Dishwasher - Slow fill

Said dishwasher suddenly began taking a long time to fill. The water pressure is OK and the primary filter at the hose connection was clean. I removed dishwasher and side panels and started machine. I could see that the water was flowing very slowly and eventually the machine started its prewash. Total cycle time is now about two hours instead of one.

The plumbing on these machines are very complicated so I need help as to where to start.

The only clue I have is that previously the filling water was audible with a varying note and then it would stop, wait a while and continue filling stopping and starting until full. Now it is a constant slow trickle.

Thank you in advance for your help.