My GE dishwasher won't drain all the way after cycles. Sometimes the water is up to the door, sometimes it is lower but never always gone. We've checked the drain lines and everything's clear. The basket inside is clean. It's almost like it drains when it wants to or that something is getting stuck and not allowing it to drain completely. During the drain cycle times it sounds like it wants to drain but does nothing. I have to flip the door switch open and close several times for it to reset it which seems to help it drain what is left in the bottom of the disher. Does anyone know what part I should be replacing on it? Is it the flapper that needs replaced or check valve? I just don't want to replace a bunch of parts that don't need it and want to get to the bottom of what the problem really is. I was thinking it could be the flapper getting stuck and not opening when it should but I'm not sure. Model # GSD5920DBB GE Profile Performance

I had a hard time finding the model # on the dishwasher and ended up having to research which one it was online but here it is Model # GSD5920DBB.