Last night, I noted that my dishwasher had completely failed to clean the dishes. Confused, I decided to investigate, and realized that the spray arm wasn't deploying. More than that, the spray arm wasn't actually properly seated in it's housing. I took the dish racks out and did some more investigating, which mainly involved experimenting to see if I could get the spray arm to stay in place and deploy. From what I have experienced, what seems to happen is that the washer turns out and starts pumping water, creating enough force to push the spray arm (and the plastic cylinder/rotating blades its attached to) up out of the housing, such that I can close the door, start a cycle, open the door after hearing a clatter, and find the unit more or less laying on its side in the water.
Alongside the plastic unit, I've got a clearish plastic ring that has a small gap in it and two prong-type things on it. I've looked at a diagram and can see where it's supposed to go, but when I put the pieces back in place, the spray arm unit still gets pushed out of place. How do I go about solving this problem?