When I bought my first camper, it was raining during the delivery. The wired Happijac remote was hanging on the rear jack as we puttered around doing something - and suddenly one jack began to extend on its own. I saw it from across the parking lot, ran over and pulled the plug, which made it stop. Some drips of water had gotten into the plug, shorting one of the buttons. This was the original Happijac remote which is a very simple thing, just 4 buttons to ground. The newer wired and wireless remote use a serial comm protocol to communicate, it should be a lot harder to fool the controller into uncommanded motion, but of course things can go wrong.
If your camper has a battery disconnect, the switch is often right at the rear door and would disable the jacks. Might be a good thing to keep that in the front of your mind when you load and unload - it would be the quickest and surest way to stop a runaway jack.