I used to keep my first boat on a trailer on the drive. My drive is a 30deg slope. Back then before I converted the garage I used to have a 12v lorry winch bolted to the floor with a remote control so I could winch the boat up and down the drive to get it hitched up. Always did this with assistance.
One day I fancied a trip out on my own, so lowered the boat down to the road (I live in a crescent so it’s quiet), I put a choc under only one wheel thinking I’d done both 🤷🏻♂️, anyway I released the winch cable and the jockey wheel moved and the whole boat span 180. It started to roll down the hill heading toward the lounge of the house opposite the end of my road. Luckily to make space I’d moved my car onto the pavement , I just managed to make it to the front of the trailer and divert it to the left where it promptly buried itself into the rear bumper of my Audi . Soon after I gave up trailering and got a pontoon berth!