How do random glitches happen on computers and smart phones when the code is perfectly fine?

Question

How do random glitches happen on computers and smart phones when the code is perfectly fine?

In:

Answer 1

They happen because the code is never perfectly fine. There are errors in any software. The code just mostly works, while in a stable situation. Once in a while something unexpected happens – like a network loss, or a hardware problem, or some weird user input – and the software might not be ready for this kind of scenario. This is when you see a glitch.