I’ve heard of that bug but never encountered it. I have had zed spawn in a few times in interiors before, but never a horde level, more of a “Surprise! I bit you in the dark and now you’re already dead.” On B42 the mod author stated it wouldn’t be out until 42 was marked stable, so a few other modders (BuchoJefe & Mickey Knox primarily) jumped the gun and added their own versions of RV Interior. I use the former’s mod, and it’s pretty solid, as it randomizes interiors. Doesn’t always make sense (like an ambulance interior in a van or box truck), but weird conversions are a thing, so I think it fits in. Adding in Vanvival makes it even more OP, unless you make it part of the lore.

Glad to see you’re playing it again on 503!