You are trusting your LBS but why?
A decent wheel guy would have rebuilt that wheel with new spokes after a few spoke failures and then correctly tensioned it.
If the guy was really good, he would have checked the spoke tensions at the first failure.
What you're experiencing is the result of just fixing a broken spoke and not addressing the cause of the spoke failures, which was a poorly built wheel. Perhaps you were telling him to do it as cheaply as possible? Penny wise, pound foolish.