Have a kitchenaid double drawer dishwasher. While running the bottom drawer the top drawer fills up with water. Had the filler valve on the garbage disposal changed. Issue still continues. Any suggestions

SOURCE: Kitchenaid Dishwasher makes jack hammer sound when filling

Check the power to the valve actuator with a meter. If the power is not fluctuation (causing the valve to open and close quickly) then the problem is likely "water hammer" in the piping leading to the DW. Water hammer occurs when a fast flow of water turns a corner in the piping. The solution is too find where the pipe is vibrating and add support. Another way to eliminate water hammer is to install a shock tube on the pipe. It is filled with air and acts as a shock absorber when the water hammers. They are available at Home Depot, Lowes, plumbing supply places, etc. Another way to make a shock absorber is to install a tee in a horizontal part of the pipe with an 18 inch+ piece of pipe installed vertically and capped at the top. Air gets trapped in the vertical pipe and cushions the vibration. You might be able to do this in the space behind the DW before the pipe connects to the DW. The shock tube is smaller and does not have to be vertical so if space is an issue that may be the way to go.

SOURCE: water in top drawer

I am not a repairman but have installed several duel drawer dishwashers. Most dishwashers have a check valve preventing backflow. Water under pressure will always follow the path of least resistance and in your case it is going into the upper drawer. Be sure the drain is open and flowing easily under your sink whether that be the disposal or a TEE. It may help if the drain line is elevated as high as it can go under the sink just before it reaches the drain. How often do you use the top drawer? Perhaps run a cycle on the hottest cycle without dishes to attemt to clean or force through any contaminants in the check valve through into the drain. Hope this helps, Ken