Appliance Repair Questions? Ask a Technician for Answers ASAP
Sorry for the delay in getting to your question.
I know you've said that you've cleaned the drain but there has to be a restriction somewhere. At some point the drain has a restriction.
The dishwasher isn't at fault.
Your drain can't cope with the flow of water so it backs up and spills over.
You can't adjust the draining of the dishwasher to slow it down, if you restrict it, you'll cause problems with the dishwasher itself.
Don't put the drain hose too far into the stand pipe, it only has to go in 2 or 3 inches.
You may well have to take the drain pipework apart to ensure it's all clear and not just a small hole through a blockage causing the water to back up.
Hope this helps