Whose side are you on?

Can you explain how a contractor “shirk” responsibility due to technicalities in an insufficient contract?

If they aren’t contracted to do something, what is the reasoning behind thinking they should do it for free?
I'm not a contracting officer, nor do I think it would be proper for me to give specifics on our contracts. A good portion of my job deals in making certain the contractor adheres to specifications and contractual requirements. These requirements sometimes come down to interpretation, which I think you could imagine.