I replaced the supply lines and mesh in-line filters. I made sure incoming water pressure was strong. I also cleared some debris from the internal drain filter down below. The F20 persisted.
My plan was to start swapping out parts from the inlet on. I ordered the valve and got it in a day.
Thanks to the schematics and videos on appliancepartspros.com, I was comfortable with the repair, and had confidence in my plan.
The actual valve replacement took about 10 minutes. Bingo bango F20 gone. Back to work wife!! j/k
Thanks appliancepartspros.com!!! You saved us a call to the repairman, and I look like a hero.