This is something that I hadn't done or that directly impacted me, but that had an effect in my life several years after it happened.
It's one of those stories that you think "this only happens to others", and then someday you're the "others".

So when I was born, I was, naturally, registered on the health care system. My parents chose an uncommon name for me (uncommon in my country) so I think I wasn't registered by the time of my birth, but 4 months later when all the bureaucratic crap came to an end (long story short, the guy that was there when it started died and my parents had to wait 4 months for another person to be appointed). So, when my parents finally went to register me, apparently, for some reason, the computer took my name and assumed it was a male name. As I've said, my name is uncommon in my country, there're probably 3 or 4 people with the same name here in Portugal.
Why did the computer assume it was a male name AND why didn't nobody check that? Since my parents had to ask to government entities to let them name me that name, I'm assuming it wasn't in their db. So why did it assume male? Was it purposely programmed that, by default, all "newly-registered" names were to be male? Was it random? Who the hell knows.
And how did nobody check that, every time I went to take vaccines? I don't think anyone told my mom that everytime we went there that the data was wrong, otherwise the situation wouldn't have lasted for 14 years.
We only knew about that mishap when it was time I had to take vaccines specifically for women and that I wasn't being noticed of it even though a friend 1y younger than me had already taken hers.

I find this story amusing but now that I started thinking about how it came to life (no pun intended) I'm actually a bit pissed off about how they didn't think of uncommon names and that how that could affect their registry in the system. They could have - IDK - placed "undefined" in that field so that it would caught the register's attention.
Moral of the story: don't assume stuff :v