I have had to replace two DEF injectors in two years due to plugging. The truck sits for 3 months in a garage in AZ in the summer. When I run it after storage the injector has been plugged each time. Dealer said there are two fixes: take it out and hammer it like it was a rental to clear the fluid from the tip of the injector or run the DEF reservoir down to low level before storage. Neither seemed like the right answer. Suggestions?