[matfil]

I actually quite enjoy the true mysteries that nobody has touched for years. It's a situation where you're expected to slink off into a corner and swear quietly for a few days, and nearly-certain hero status if you pull it off.

The more frustrating situation it needing to jump in and make a one-off fix to something that is at least notionally "modern". These can be just as impenetrable, but you have to hold your tongue much more (especially if some of the developers are still around), and there's generally a lot less kudos for sorting things out. Personal "favourite": debugging stuff that's virtually impossible to build locally "...because we've got this great CD pipeline".