What do you do if you notice your contractor's production plans do not match your consults drawing plans?

i will determine the reasons of this delay and i will ask the contractor to update his plane. 

There is an official stage called shop drawing approval, where the consultant wil review the shop drawings and put all his observation. Once done, the Contractor rectifies his plans, until he gets consultants satisfaction.

Only when the shop drawings are approved, the contractor is allowed to start building with them.

First you should order him to stop immediately, then know from him who gave the order for this change and why, if the order came from the project manager or his administrator and it was reasonable, ask them to notice you next time when changing anything, if not, stop everything and solve the managing gap, because there is a gap here.

Anyway, After solving the gap issue, you should redraw what the contractor built, and make a meeting to decide whether you'll change the plans according to reality or demolish and rebuild the bad part on charge of the contractor.

If it's a shop drawing plan to the design then it should be that way if there is an editing ( like adding some components then you should check from them why is that ) cause sometimes i do that but surely  with  the approval from the consultant 

if you have regular (frequency of meetings upon Project duration) Project meetings, then there is lesser likelihood of delays except due to "act of God". If at all there are delays then sit with the contractor to revise the plan. First preference should always be to ask contractor to put in more resources without changing the previously Target date. 

Thanks for the invitation

Good question

Well...Agreed with both answers given by

Mr. :Labib & Mr.:Dhara as well too