I've had the Firgidaire stackable laundry center since September 2000. It has always performed perfectly. Two weeks ago I washed a small load of shirts. I changed the water level on the front of the machine to small just as always. Since then, even though I've changed the level back to full or large load, the washer is "stuck" on a small fill. I can hold the knob over on reset and make if continue to fill, but this is an extreme pain at times. It does the same on the rinse cycle. I have to be sure to catch it in time to make if continue to fill or the clothes don't get rinsed well.

What could possibly be causing this?

Lynn