Tailgate Troubles!

Well, it wasn't the best of travel days. We have headed out on our next adventure in Michigan and New England. On our second travel day, we pulled over after about an hour-and-a-half of driving for a quick break and like all stops the first thing I did was walk around the front of the truck and head for the camper door doing a safety check along the way. I check the tires, look for loose items, check for things hanging down, confirm the pin is locked, etc. This time, as I approached the back of the truck I noticed that the tailgate was down and our generator that we lock into the back of the truck, was perched precariously on the tailgate! It was just inside the sides of the bed so it couldn't be seen in the rear view mirrors.
Sometime along the brutally rough interstates we had been traversing, the tailgate dropped down on our Ram 3500 and the stuff stored in the bed of the truck made their way back. We have the generator locked into the bed of the truck to prevent theft, but it's locked to a tie down at the end of the bed with a 6' cable. Had it fallen out of the bed, it might have beat the crap out of our truck and trailer as it slowly disintegrated on the roadway. Once the handle let loose where the cable holds it, the little engine could have gone under the wheels of our RV or hit another vehicle on the road! Thank God we stopped when we did for a break.
There is a recall on the Ram trucks to have the tailgate latch checked which we had completed. We called the dealer to confirm that ours passed the check a few years ago when the recall came out. To help prevent this from happening again, we took another ratchet strap and ran it across the back of the bed in front of the gate to create another barrier that should keep things in the back of the truck if the tailgate deploys again.
We also tested our truck to be sure we couldn't have accidently lowered it by putting the truck in drive and pressing the tailgate button in the truck and on our key fobs both of which generated errors on the dashboard stating "Not in Park" as it should. We have no idea what else could have caused the uncommanded opening of the tailgate but now a new fear has been unlocked!
When we are driving, I have a standard cross check. I look at the road of course most, try to catch some of the views outside, check the side mirrors, quick scan the dashboard for issues, check the engine temp (we had an overheat issue a while back so that gets a special look!), occasionally flip over to the tire pressure screen in the truck and back, glance at my phone for the RV tire pressures and NOW I am adding a quick glance back in the rear view mirror where I can just see the top of the tailgate if it's closed properly!
Anyone else ever have issues with a tailgate opening while driving!