My LG dishwasher experienced a number of issues including intermittent drainage. So I finally removed it, set it up in my garage and tore it apart. First I replaced the tiny, burnt out pump motor. Then I checked the overflow switches and by accident I discovered that there is a backflow valve in the drain hose that is essentially a plastic ball, that was stuck over the outlet. I pushed the ball free with my finger and the dishwasher drained correctly.
After reinstalling the dishwasher in the kitchen, things worked fine until I switched back to the "goo" dishwasher soap and again I had to pull out the dishwasher, take off the side panel and unstick the ball. As long as I used dishwashing tablets or power the backflow ball did not stick.
Unfortunately, the door leak (I had to use a c-clamp on the upper left corner to keep it from leaking on the floor) on the LG got so bad I replaced the LG with a good Whirlpool.