Thank you for letting me know. Do you happen to know what job role the vampire is in? Is this during the actual vampire invasion event where they break into your played sim's house or apartment (it might be called job_VampireVisit or Nighttime_Bite) or is it during the outdoor walkbys where they're hunting through the neighborhood?
San Myshuno has some unique coding from the game devs - they made it to be a vampire hunting ground already, essentially, with a LOT of walkbys. There's almost always a vampire running through. I do have a cooldown that's supposed to prevent vampires from going haywire, but it sounds like that's not working if a lot of sims are in the target distance more or less at once. I'll figure out a fix for that. The spellcaster thing I'll also investigate and get a bugfix for.