One of my favorite stories showing the importance of coordination of drawings and specifications is about documents we received from a landscape architecture consultant. The number of large trees is commonly indicated on the drawings by images that can be counted; for example, large maple trees would be represented by tree stamps (or the digital equivalent), one per tree. Another way to show the quantity of trees or other vegetation is a schedule on the drawings that shows the number of plants of each type. A third method also uses a schedule, but one in a specification section rather than on the drawings. In this story, a landscape architect had used all three methods, so we had tree stamps, a schedule on the drawings, and a schedule in the specifications. Each showed a different number of maple trees.
Another example of information appearing both in the specifications and on the drawings comes from structural engineers. I don't know if this is universal, but the ones I work with like to put a lot of information on their drawings. In most cases I don't have a problem with that, but the same engineers typically edit specification sections that contain some of the same information. And, as you might expect, it differs from what is shown on the drawings.
Finally, elevator specifications written by elevator consultants commonly specify the number of floors, the number of stops, the number of doors on each floor, the locations of doors, the type of door operation, and the travel distance - all of which can be ascertained from the drawings.
These three examples are fairly obvious, yet persist. Other redundancies are hidden in the many drawing notes; they repeat or conflict with information found elsewhere on the drawings, or with information in the specifications.
I believe many of the problems we see come from an honest effort to make sure the job gets done correctly. Most of the time, team members don't understand how construction documents should be organized, what should go in which document, and how to state requirements; they also are not sure what other team members are doing. Each person tries to make sure everything is covered, by entering information in many places. The result is a hodgepodge of notes, which often disagree with each other
Design professionals are justifiably concerned about contractors' ability to coordinate subcontractors; they should be just as concerned about coordinating the location and format of the information that appears in the contract documents.