We recently had a problem with our dishwasher -- it wouldn't drain. Merely scraping stuff off the bottom of the washer didn't help. I pulled the rotor out, and took off a housing above the motor, but this didn't reveal lots of gunk either.
I tried running with white vinegar and baking soda. I think it cleaned things up, but still water at the bottom.
Next I took the baseboard off and unconnected the drain tubing. This allowed water to drain freely, so it looked like things were draining from the washer fine.