1 hour ago, zztong said:IIRC, a zombie volume doesn't place it's zombies until you're within 4 blocks horizontally and 0 blocks vertically. Perhaps that code needs an exception for Wandering zombie volumes?
When I tested this, it was on a sleeper volume in a POI I had made that goes right up to the edge of the room where an open "doorway" into the other room is located. The zombies spawned before I could see them (probably that 4 block thing) but didn't activate until I entered the volume. If they also activate when they spawn for wanderer volumes, that would work will, I think.