If that guy has any way of making a mistake, he will.
If it can happen, it will happen.
Anything that can go wrong will go wrong.
If there’s more than one way to do a job, and one of those ways will result in disaster, then somebody will do it that way
If there are two or more ways to do something, and one of those ways can result in a catastrophe or pregnancy, then someone will do it.
Anything That Can Possibly Go Wrong, Does
‘Everything that can possibly go wrong will go wrong’
It is impossible to make anything foolproof because fools are so ingenious.