Happens to me too. I get wraiths and possessed armors in the mine track. I currently have it switched to the snow biome on the Ultimate 5.0 map.I'll check the map I offered as a download to make sure no background walls are missing - perhaps some were dislodged. If the entire bottom area is walled in then the wraiths can't get to you. The map I'm running right now works fine, and I even let the surface grinder go for an extended period of time in the past few days to get another one of my newly-built farms to spawn a large quantity of crystal shards. I'll look into it!