I’m a relatively new player who doesn’t play with wander spawns turned on, but I too observe this behavior (zombies popping up out of thin air). It seems linked to sound/noise: running over a pack of zombies with an APC just seems to make bigger crowds of zombies (and having scoped out the streets first, I know additional packs didn’t wander in—they popped up out of thin air), but any activity (like dismembering corpses) or even killing one zed with a sling causes a few new zombies (sometimes inconvenient ones given the unpreparedness of my character) to spawn … again, out of thin air.
I’ve thus far played with minimal mods (just NPC-needs-off/whatever-it’s-actually-called and boats) and, again, never with wander spawns turned on. I managed a fairly long run in original Danny (before desire for a constructed smoking rack made me seek current builds) and never noticed this behavior.
