I once fixed a bug in Kolf (the KDE mini-golf game) which was about the ball glitching through walls if you hit them in the right angle. The patch that fixed the issue was rather huge, since I ripped out the home-grown collision detection and replaced it with a standard 2D physics library.

Sadly, my patch broke some custom levels which relied on the glitch. https://xkcd.com/1172/ is more true than you'd expect.