One time in Fallout 3, I'd finished the Blood Ties quest and fast traveled to Arefu to get my XP reward from Evan King.
Weird thing happened: A Raider somehow spawned in Arefu. And no, this wasn't the weak Raider with maybe a sledgehammer or a 10mm SMG, it always spawned with a Combat Shotgun, Assault Rifle, or something else. It would murder Evan King with ease mere seconds after I'd arrive, then the game tell me I failed that quest, that I was now an enemy of everyone in Arefu and The Family, and that all the work that I did was for naught because the game decided to flip me the bird.
So, I spent literally the next ten minutes reloading the auto save when I fast travel to Arefu, taking pot shots at the Raider, and hoping that I would kill him faster than the Raider could kill Evan King.
Got the Raider eventually, but it was way too frustrating, and the next time I went to Arefu (to steal the Repair Bobblehead), ANOTHER Raider appeared and murdered Evan King. Fuck Arefu and fuck the Family, I don't give a fuck that he died because the game felt like spawning Raiders in a town.