Trusses dont have the ability to have a z offset value like Beams and joists.
If a truss (as is normally the case) needs to be offset from the roof level so that a purlin can sit on top, then the Start level offset and end level offset need to be adjusted. This breaks the link with the level preventing purlins from automatically adjusting their graphicall end offset in plan and breaks the analytical model preventing alnalytical linking to analysis software.
Solution : Add a "z offset value" Similar to Joists and Beams (See below)