1 year old Frigidare dishwasher we've had issues with it draining ever since we bought it- should have returned it. Sometimes it will drain completely other times there's 2inches of water sitting on the bottom. Sometimes the water comes through the air gap fast other times it just trickles. There is no blockage in the drain line. I replaced the drain pump which did not resolve the issue

If I notice it not draining correctly during the drain cycle I will open and close the door a few times until it begins draining properly.