Plot-Sensitive Latch

Locks usually function just fine, but sometimes they burst open without any obvious immediate cause. In media of course this happens because the plot demands it, though it is occasionally deliberately used by a Con Man. This is typically at an inconvenient or embarrassing time (they grabbed a suitcase identical to theirs but filled with sex toys, which bursts open as they run 15 minutes late to a flight). Sometimes handwaved by having the container stuffed with something (say, money) that presses from inside, but that doesn't account for the timing.

Not related to Plot Lock, which is about being forced to progress through the plot in a desired order. Sister Trope of Plot-Driven Breakdown; this can be reclosed immediately, though the contents may take some work.

Film

 * At the beginning of the first Eden of the East movie, Saki's suitcase bursts open as the cabbie manhandles it, spilling guns and ammo and grenades onto the ground- not hers, but a setup by another character. How they got the suitcase to open at exactly the right time, though...
 * In Meet the Parents, Ben Stiller's suitcase gets lost in-flight. A suitcase is found matching the description and delivered to him (at the parents of his girlfriend). He attempts to open it but can't and leaves for the day, leaving his prospective father-in-law alone at the house. Being former CIA he opens it easily and finds it full of fetish and bondage gear and sex toys.
 * Happens in Matchstick Men.
 * At the end of It's A Mad, Mad, Mad, Mad World the suit case carrying the money pops open, dumping the cash into a crowd of people.

Literature

 * Near the beginning of The Chronicles of Narnia: The Silver Chair, Eustace and Jill are escaping from some bullies towards a door that is always locked, and of course it turns to be unlocked. Justified in that Aslan has magically caused this to happen, but they don't know it at the time.

Live-Action TV

 * Sawyer of Lost uses it repeatedly, to the point of lampshading when we encounter an alternate universe where he's a cop.

Western Animation

 * The SpongeBob SquarePants episode "Krabs Vs. Plankton". Mr. Krabs is sued by Plankton for slipping in the Krusty Krab, and his lawyer is indisposed, giving SpongeBob his briefcase, which he claims contains everything necessary to win the case. Unfortunately, the lawyer neglects to tell SpongeBob the combination to the lock, so he spends most of the trial struggling to open it. At the last possible moment, the briefcase opens, revealing