I've run into that issue myself, as a fellow servo player, and it is a pain. Unfortunately, the devs hardcoded the sleep test into the vampire invasion situation in Sims 4's Python layer and it cannot be changed in tuning.
Hypothetically you could create a nearly identical replacement of vampire invasions built on a different type of custom situation, but it'd require about 20x the work. If I end up doing an overhaul of vampire invasions this is on the list of things I'd fix.
I did some tinkering and just found out this:
Vampire invasions will happen with a servo in the household as long as the servo and every other household member is asleep in bed. You have to click recharge on a bed and not the servo itself.
But then I'm running into another issue: the servo with the defence module turned on would not autonomously zap the invader. It wouldn't even zap when I tell them to.
Is that fixable? Could this be caused by the mod?
You've gotten farther than I have with this - I did take a look at the coding and at first glance I don't see anything in the tuning or in the Python layer for either invading vampires or on servos that would prevent servos from being able to zap vampires, unless the specific vampire you're trying to zap is pregnant.
From what I remember, vampire invasions were broken before Discovery University launched and were left that way by design (as per the bug report forums), so I doubt this functionality was ever actually tested by the dev team.
