I’ve been living in a bubble with my .NET day-job, where debugging/tracing/postmortems are a breeze. Compare with, say, a CORBA or DCOM system, deployed to prod with uber-optimized binaries without any debugging-symbols.

So it’s not that I haven’t worked on large-scale, complex legacy systems - but that I haven’t worked on any large-scale, complex legacy systems written in languages bereft of runtime reflection and verbose error reporting.

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It’s also possible that the bug was never found because its impact was so minimal: e.g. 1 crash per year, each causing 3 minutes’ downtime in a noncritical system: that’s something that will never get investigated fully.

Sorry but I don't buy it, any crash can be found and fix by one or more humans, if it was not it's either they're incompetent ( I doubt that ) or they did not beleive it was important enough to fix.

A crash is actually the easiest kind of problem to fix since you have a crash. It means stacktrace, core dump, kernel error etc..