I only did the cake experiment, because is was a challenge by Sears at that time, if it would not clean everything out of the machine at the end, I would get the machine for free, although redundant, getting a free machine that doesn't clean.....but more along the lines of the performance of this machine.....
were not going to go into the ideas of water temp, detergent, and cycle used.....this you have already checked out.....
but I am concerned something is not operating inside correctly....and something in the UltraWash module may be plugged up or blocked, possibly not allowing full water flow......
you can always remove the bottom basket, and unscrew the lower wash arm, using a popcicle stick, or something similar, to trigger the switch and start the machine with the door open, just to make sure you are getting full force of water up thru the port.......
these modules/motor/pump are so simple to remove its not even funny......basically remove a hose, backflo, and turn four clips...and pull out from the topside.....
not normal for one of these machines, but something as simple as a block holes in either wash arm can hinder performance......it could be something so simple your not realizing or seeing yet
let us know how your making out!