What board are you using?
She is using the same desk the designer used the previous time. This is the point the designer was making. It is possible that the designer was unaware of the problems because his/her electrician fixed it prior to their arrival. It is also possible the board was already set to a slower DMX rate. It is such an easy fix there is no reason not to give it a try. Oh, and never listen to the designer when it comes to troubleshooting a rig