Not long ago I bought a used Canon EF 400mm f/2.8L IS II in great condition off of eBay (it was pristine). For kicks, I took it outside to the street in front of my house and took some pictures of the moon. When I was finished, I hoisted the tripod, head, gimbal mount, and lens on my shoulder to take into the house where I have to traverse about 5 concrete steps and a concrete landing/front porch that lead up to my front door. As I stepping up to the 3rd step, I could hear the lens foot slowly but surely slipping out of the gimbal mount -- I had forgotten to tighten it fully after balancing the combination. I cringed and waited for the inevitable sound of my most expensive lens bouncing off the concrete steps after a 6' drop.
*click*
I opened my eyes and looked over my shoulder. The lens was still there. It had been stopped from falling by the set screws on the bottom of the lens foot. I've never been so thankful for a $0.10 piece of gear...
And another story... I typically shoot the championships for a local recreational sports club. In addition to being paid, I also get to play in the league for free. On a couple of occasions, my team has made it to the championship game, making photographing the game especially challenging. One one occasion, I handed my camera and EF 70-200mm f/2.8L IS II lens to a fellow player (who wasn't playing in the game), gave him a 5 minute rundown on how to shoot the game (I set the exposure controls and locked them but showed him how to place the AF point over a player, half-press, track and shoot).
At the end of the game, I was in the dugout (with a concrete floor) and he handed me the camera and lens. I set it down on the bench and he left while I packed up my things. When I picked up the camera and lens, the lens separated itself from the camera. In an instant, I had a choice -- do I prevent the camera from hitting the ground or the lens? I instinctively chose the lens and caught it, but my R6 hit the ground pretty hard. Thankfully, it was functionally ok, but it did get a few battles scars from the drop. I have no idea why the player chose to push the lens release button, but he must have been curious about it. The lens was decoupled but still attached; something I never would have thought to check.