Mine has done that on occasion. I figured it out after pulling out of a campground, making a turn onto the highway and having the tires rub on the fender. They rubbed enough to take a chunk out of it.
After I start the engine, I turn the power on the jack system, hit retract all, let it cycle, then turn the power off. Then I check to make sure they air bag system is engaged. I check this before driving off every time now.
I'm not sure that is the correct procedure with the chassis, or why it works that way, but that is how I make sure they are working.