I had an E21 error. There was a blockage in the boot feeding the pump. It was a plastic part that I am sure is a part of the machine. It also had a sock in it. The boot has two inputs. The big one comes from the drum and there is also a smaller one. I think this part came from the smaller input hose but I don’t know the orientation.
Look here for picture of part. Pictures by lou0524 - Photobucket
Found it. It is the filter that goes in the drain hose.