i've ran into that problem before, i just changed recievers and it cleared up, same model reciever, same wiring routes. haven't got around to sending the reciever in to be checked out yet. if you think it's something bench related, you might try holding the model in your hands and letting someone else work the xmitter, or vice versa. also you might conside range checking the model again (might not be the problem, but it never hurts)

keep us informed
Kevin