2004 Itasca Horizon, Fisher and Paykel dishwasher. Dishwasher is in kitchen slide underneath the stovetop. The dishwasher works OK, but when we empty the kitchen sink suddenly, as in pulling the stopper after washing dishes in the sink, we end up with water standing in the bottom of the dishwasher. The sink is not part of the slide but stands next to it. I assume there is a drain pipe somewhere that is constrained or partially clogged, but I don't know where to look. Thanks in advance for any advice.