My 4-year-old will often do things like lean on an open drawer or stand on something that isn’t designed to support his weight. When interacting with a man made object, it’s useful to ask: What is it made for? My advice for my 4-year-old would be to make sure it’s a trampoline before you start jumping up and down on it.
Don’t expect things to be good at something that they weren’t designed to do.