I had this same situation on our Miramar, the factory installed the cabinets right on top of the duct work cutting off almost all heat flow and forcing into the bathroom. Bottom line is that I cut the ducts on both sides of where they were crushed. I then installed a plastic pipe ( new sewer connection fit) and hose clamped both ends together to complete the flow. There was more than enough duct to stretch out and make this connection. I just rerouted the new setup. Works great now.