I O/Oed semis for over 30 yrs and before I ever move from switching trailers I always grab the johnson bar and gently lurch the truck forward to insure that the brakes work and the pin is locked. thats One reason why manufactures have those little safety pins on your RV hitches that your supposed to use to lock your handles in place. One to make you as the operator get out of your truck to ensure your pin is locked. During my travels on the interstate several years ago on I5 above Stockton I witnessed an RV 5th wheel disconnect on the otherside that I was traveling. Of course the tailgate blewout and with no safety chains it locked up the itres as it careened got sideways and rolled leaving debris flying in all directions and across the freewy towards us. Poor guy not only lost his trailer but as I passed by his bass boat was plowing up the median. Now thats having a bad day.
On another note about disconnects, my own experience and being lazy about
checking all my RV rig I had left my home and travelled 4 or 5 miles when my trailer tried to exit my truck after a hard bounce but it wasn't the kingpin connection. I had the over the wheelwell style brackets and one of the retainer pins had fallen out (no hairpin clip was installed) causing the whole fifthwheel to come out out one of the saddles. Thankfully it held on the other side long enough to get stopped and get the jacks on the ground. I lost only a straight bed rail. I was mad at myself but glad no innocent people were hurt. SO
check every pivot/attachment point of your rigging, not just the kingpin...