When you overclock you add voltage which helps with this which goes a long way. You would often hit thermal limits first, so heat dissipation is a major factor.
This causes heat and load spikes, and while you get no errors, the increased frequency doesn't give you any real world performance gains. Returning a to a slower configuration actually gives a much snappier and performant system.
It feels unfair to generalize across time and architectures
I stopped overclocking systems after Athlon XP. This is why I gave that example.
Even without overclocking and overheating, I've seen and still seeing partially cooked processors which shut-down half of their FPU pipelines to stay reliable albeit with orders of magnitude lower performance.
CPUs are much more complex with their MCE and more advanced microcode structures ever, and there's much more than meets the eye.