I have a GE Triton Dishwasher that will drain, I hear and fell it drain, but will not drain the water completely out. It will leave water up to the elements. I have checked the fine filter at the very back, bottom of the dishwasher and found nothing. I checked the piston and nut assembly and it looked perfectly fine. I took apart the sump and found nothing down int he hole. It was very dirty water though.
Disconnect the drain hose from the house plumbing.
Often it will clog where the hose goes over the fitting.
You could try draining it into a pail to eliminate a house plumbing clog as the cause. Just be sure to hold the drain hose securely in the pail and put a towel over it’s top, unless you want a shower.