(Mod Help) Rim of Madness Star Vampire "attack"

So, I have a fairly heavily modded game (no surprises there) and had an event where a Star Vampire came to visit.

I say visit, because it sat to a side, did nothing, and eventually died of starvation.

I was lucky/cheaty enough that it showed as a hostile on my minimap or I'd never have seen it - they're invisible, apparently, until they attack. I had a colonist toss about 30 molotovs on it to no effect, while snipers pelted it with bullets (also no effect), and called down a MiningCo airstrike on it.

When it finally died (on it's own, mind you) the combat log showed up with entries detailing the attacks, but it had taken no damage - the sole entry in the health tab was pretty much "Malnutrition - Extreme 100%".

Current base is set between mountains, with walls and fences to limit ingress points, and numerous turrets to provide fire support. I thought maybe it couldn't attack because of pathing, but even with four colonists outside attacking (snipers + grenadier) it just sat there.

Any ideas on what should have happened, or what went wrong?