The first is preventative; to examine systems and see what can go wrong and, as far as possible, to find ways to ensure that the systems are sufficiently robust.
When I’m doing that, I’m the Glitch Finder General.
The second is responsive or reactive, addressing things after they have gone wrong. I’m repairing things in the hope that anything potentially terminal can be headed off.
On the days I do that, I’m the Glitch Doctor.
Two sides of the same coin.
Probably best to have things identified and, where possible, fixed before they go wrong, though.