I'm looking for a single word that would be used to describe someone who is an incompetent intermediary. To be more specific I would like to describe someone whom it is necessary to communicate knowledge through, however this person doesn't have the proper skill set to understand or further communicate the knowledge accurately and effectively.
As a hypothetical example, consider a scenario where an engineer communicates technical knowledge with a program manager, who then attempts to communicate that knowledge with a customer. However, because the program manager lacks technical prowess, the relayed message is distorted to the point being mostly or completely wrong. What word would one use to describe the program manager? Preferably I would like to find a non-pejorative term.
Edit I would also be interested in any phrases that describe such a person.