Electrolux Epic 6500 SR vacuum loses suction w/hose attached?

The vacuum was working fine. While running, turned down the dial on the top of the machine. Immediately the vacumm shutoff. If I turn it on without the hose it runs fine. Attached the hose and it shuts off. Saw on another repair site that the hose leading to this dial had collapsed or become clogged. The author said to remove the side sliders, lift the top and repair this small hose. I can not get the side slide off. I have tried numerous methods and tools but it will only slide ~1" in either direction. I am afraid if i apply more force i will damage the housing. Any suggestions for removing the top housing?

Bob D.
March 2010