@teamnate I am somewhat surprised by the action of the repairman. There are issues with the pressure dome obstruction that can cause the DRN error. A technical bulletin on how to check and fix this was published. Check it out and see if that resolves your issue. Of course, you also want to use a Shopvac and blow air through the pump into the drum to clear any obstruction between the tub and the pump. Just in case…
Here is the service bulletin [document|25951]