Try this:
Disconnect the electricity to the dishwasher. Remove the front door panel by removing the 4 screws..2 on each side on the inner edges of the door. Close the door and you'll see the detergent dispenser from the outer door. There is either one white arm with a hook or two. When you turn the dispenser the white arm moves and hooks into a bi-metal strip bar. At the point when the dispenser trips, the bi-metal bar bends and releases the white arm. Over the years it might have become mal-adjusted. Put a drop or two of WD-40 onto the bi-metal bar and also on the tip of the white arm where it hooks. Then, from the inside of the dishwasher...turn the dispenser and latch it. From the outside now, pull down gently on the bi-metal bar to see how difficult it is for it to release. At this point you can bend the bi-metal bar to adjust it accordingly so it won't take so much effort to trip the white arm. Try this out and see if it corrects the problem. I have done this many times and it has always worked for me.
