I also ran into something like this, being young and straight out of university. The company I worked for at the time basically generated a 2.5 million line XML file that would be sent to various parties to be transferred to get the data that was relevant to them.

I was responsible for changing the generation of this file (in Oracle PL/SQL ... yuck) to a new schema which was vastly different. Needless to say I just silently ignored a lot of bugs which I kept justifying myself weren't real issues because we had a massive time constraint. I'm talking 100 hours of dev work in a month type shit. Well I managed to offload all the problems onto the client in the end because it turns out they had introduced a fair share of issues themselves (they were the ones that came up with this schema). It was pretty shite though and I'm glad I don't work in that kind of toxic space.