I bet you have something stuck in your drain pump... I have only worked on a few of these. But from what you are describing, I bet thats it.
To warn you, they are, lets say, Intresting to take apart.
Maybe one of our other techs can get you a service manual.
To gain access to the drain pump, the power must be turned off to the machine, Disconnected from the cabinet and slid out. You gain access threw the left side of the unit, by removing the outside side panel. The drain pump is located in the front left corner mounted on the sump assy.