Design of Truss/Purlin in Staadpro

I am facing a problem while designing a roof truss.

While designing the roof truss as a whole, the purlins are failing in output results on analysis 

But passing when checked by selecting the beam individually.

Also when the purlin is designed individually alone with same properties and loads its getting passed. Kindly find the attachments for understanding the problem.

Regards,

Akshay Rana  

                      whole roof truss.std     purlin.std