Put this clip just before the mishap in your edit, after the knowing look and before the collapse, so it bridges the setup and the payoff. Follow it with the fail sound when the plan lands badly, and save the knowing line for the moment a character spots trouble coming.
About this sound
This is a very short cartoon drum roll, lasting a fraction of a second, with springy percussion that bounces and stops almost as soon as it starts. It feels playful and deliberately silly, like a tiny musical wink for a clumsy moment. The clip comes from the 1941 Donald Duck cartoon Timber.