If it is like my Kitchen Aid which has 3 levels of spray arms and an adjustable height top basket, look at the water manifold on the back. The middle spray arm should engage a hole to get water. However in the adjustable height basket version, there may be 2 holes-- an upper and a lower. The water pressure is supposed to push a seal against the unused hole when operating. If this seal is not working, then a large amount of water will come out of it decreasing the pressure to the point that i might partially work the middle arm, but not have enough pressure to work the upper arm. To experiment, you could put a cork in the unused hole and put a tie wrap around it to hold it in and see if everything works after that. If it does, then you may need to replace the manifold. I have a similar scenario where I am suspicious that not enough water is coming out of the middle spray arm to clean out the soap dispenser leaving lumps in it. Hope this helps.