what may be cause of the unexcepted deflection (at the high roof-low roof juction) in a steel structure?

A car service station is modeled with high and low roof truss structure? I have tried with and without releases. There is excessive moment and axial force. Because of this unable to specify the member as truss member.Have attached the deflection diagaram of my staad model. Unexcepted huge deflection occurs under nodal dead load and liveload .I have tried including more number of intermediate columns and increasing the section sizes (circular hollow section - tata structura). There was no improvement .Please help me how to resolve the structure from failure. what may be mistake or problem in modeling??? please help