I am trying to clean my dishwasher out. I have a kenmore ultra wash sensor atc quiet guard 2. There is a screw I need to take out in the bottom, but a black plastic piece turns with it, looks like it may have a hex head (made of plastic) to attach a wrench, I have tried some force, and am damaging the hex head but I am afraid I will break it. It is not allowing me to loosen the screw so I can clean further. What is up with that and how do I loosen it?