Random NPCs only spawn in the central overmap

[RydellV]

Describe the bug

Random NPCs only spawn within the central overmap. If the player travels away from that overmap then random NPCs will not be encountered.

Steps To Reproduce

1. Create a fresh world with random NPCs enabled, set random NPC spawn rate to 100x.
2. Create a character and wait 6 hours in game.
3. Check your debug.log to see random NPCs spawning in the starting overmap.
4. Teleport several overmaps away and wait 6 hours in game.
5. Check debug.log again to see random NPCs still spawning only in the starting overmap.

Expected behavior

Random NPCs spawning all over the world.

Versions and configuration

• OS: Windows 10 Pro
  • OS Version: 10.0 1809
• Game Version: 0.D-11532-g0696252 [64-bit]
• Graphics Version: Tiles
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food]
  ]

Additional context

Possibly related to #35146

[Inglonias]

On a whim, I tested this and sure enough, this seems to be the case.