It COULD be convincing to your client if you showed them this discussion. It's not like all these installers all over the United States and Canada are bogusing up a discussion just for your particular client! It's a fault of the equipment which is to say the manufacturers and we're trying to fix it for lots of people.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw