The lower spray arm has a rotating spray wheel on the end of the arm. The wheel spins freely and so does the arm. The problem is when the cycle is running, the arm stays in one place while the spray wheel spins. The arm should rotate around. It's not stuck, I can move the arm, and if I do and close the door again, the arm will rotate one time and stop in the same place. there's nothing blocking the arm that I can find. I've cleaned all the lower arm parts and can confirm there is no food blocking the water.

There's a plastic part that locks the spray arm assembly to the bottom of the washer. I can be locked in place in 2 different places (180 degrees opposite). If I put the plastic part on the opposite side, the spray arm will then stop in a different place, but will not rotate around during the cycle.

I've had a repair tech look at the washer but couldn't find what the problem is.

Appreciate any help. thanks