Vette Racer, ask them about a DEF pump recall. While on our way to Phoenix last March I got a message on the dash "incorrect DEF detected". I had had just filled the DEF tank at LOVES the night before in Amarillo. Dodge garage in Albuquerque determined my DEF pump was on it's way out and NOT bad DEF. He said they had a bulletin on them and he thought Chrysler would be recalling them as he had 5 3500s in at that point for replacements.
Since having the DEF pump replaced I've been using a LOT less DEF. I'd at least ask about "bad" DEF pumps even though you haven't thrown a code on it.
Dan