Buddy of mine from town changed a propane bottle on his travel trailer just before a trip couple years ago. Forgot to tighten the hold down clamp. With wife & 3 small kids in truck headed down the highway....20 miles into his trip another motorist cut in front of him and forced him into a stop. One of the two tanks had dislodged and was jammed under the front trailer axle , grinding along and spraying sparks everywhere according to the other motorist. It must have just happened as those tanks are very thin-walled and it never ground through. The hose had broke but the bottle valves where closed luckily.
The fellow is a pressure vessel welder and he is known for being very thorough in everything he does ....but an instant of inattention could have been catastrophic here.