"You can stand in line till da cows come home and da slow customer at da service-desk is still not gonna budge, but da moment you decide to plop down and comfortably settle yer tushie on da floor, DAT'S precisely when da line will start to move again, and then you'll hafta hastily "up, periscope!", putting even MORE strain on yer achy leg-muscles!
Carrying a skateboard to sit on can allow you to somewhat alleviate da "Murphy's Law of sitting down" debacle, since you can scooch yerslef forward more easily without actually having to groaningly stand up again, but unfortunately, many stores/offices take a dim view of bringing wheeled toys into their checkout-lanes or waiting-rooms! :P
The tension between certainty and justice. Law strives to be a system of clear, predictable, general rules applied equally to all (certainty). But justice often demands consideration of unique circumstances, intentions, and contexts (equity). The hard problem is that these two aims are in perpetual conflict. Applying the rule rigidly can lead to unjust outcomes in specific cases ("The letter of the law killeth"). Allowing too much discretion to judges to achieve equity destroys predictability and opens the door to bias and arbitrariness. The system can never fully satisfy both masters.
Example: A law says "No vehicles in the park," meant to ensure safety and tranquility. A rigid application would ban an ambulance entering to save a life, or a veteran's WWII jeep in a memorial display—both absurdly unjust outcomes. A judge allowing them uses discretion, but then where is the line? What about a skateboard? A remote-controlled car? The hard problem: The moment you write a rule, you create loopholes and hard cases. Law is an attempt to capture fluid human conduct in a net of fixed words, and much of what matters always slips through the holes. Hard Problem of Law.
Problems exhibit natural turnover: a substantial portion disappear not through solution but because new problems arise, or because changing circumstances eliminate the problem altogether.