You have a partial restriction in the drain. Start with the easiest first . If the drain goes to a garbage disposer - right at the disposer connector is a common place for a clog. See if you can stick a screwdriver in that hole. Next check the drain hose for a clog and finally at the drain pump of the dishwasher which requires pulling the dishwasher out to gain access there.
Tom. It will probably a day or two before I can try out the possible soolution you have suggested. So i'll try to get back to you by Friday the 3rd of May. Thank you for the fast service, and I hope it works cause it sounds easy.
I'll look for your response