Done that the once. Was my own deployment script, written and tested and safe, full ROLLBACK in case of things going amiss.
I was so confident of it I left it running and went on my lunch break. Came back to find chaos. I don't remember all the details now, but we'd been working with an offshore team whose code I'd plugged into mine as it had been peer-reviewed and approved. Turned out that it fell over because "Germany" isn't the name of a language and my code had a hard-coded list in it with no failsafe. Very much tail between legs for me, though it taught me to anticipate absolutely anything in your "sanitised" datasets. When we looked closer at the other values for language names that the outsourced team had shipped, we also found "DenMark" and "Janpanese". ¯\_(ツ)_/¯