I just received the food chopper assembly for our Whirlpool dishwasher (Part #8268383); however, it appears to have a problem with assembly. There is a flat washer between the chopper blade and the screen, which prevents the blade from contacting the screen. In one of the posts, the home repair person was discussing putting this assembly together. I found this puzzling, considering that the retaining device (not sure what you call it) is not designed to come off once it is on...unless I am missing something. Is there a method to disassemble the food chopper, or should I return it for replacement?

Thanks!