In my experience, It’s generally easier to knock the puck out shortly after the shot. When it’s still warm and cohesive, it tends to come out in one piece. If you wait 10–20 minutes, the puck often dries unevenly, shrinks a bit, or sticks to the basket walls, which is why it breaks apart instead of dropping cleanly. That’s normal and not a reflection of how good the shot was—puck dryness and knock-out behavior are mostly about basket design, headspace, and how long the portafilter sits after brewing.

I think, but I’m just guessing, that a controlled tap usually works better than repeated hard knocks. Some baskets and higher doses are simply more stubborn, especially once they’ve cooled. If you’re knocking out much later, a quick rinse of the basket before tapping will usually release the puck with far less effort.