1.6.6 World map problem

[Targuil]

I came back from the East on my Arcane blade, did Daikara backup guardian and Temporal Rift. When I exited back to world map and took a turn the game started to throw this Lua error to me at an increasing rate:
Lua Error: /mod/ai//worldnpcs.lua:38: attempt to index a nil value
At [C]:-1 __index
At /mod/ai//worldnpcs.lua:38 runAI
At /mod/ai//worldnpcs.lua:52 doAI
At /mod/class/WorldNPC.lua:155 act
At /engine/GameEnergyBased.lua:129 tickLevel
At /engine/GameEnergyBased.lua:64 tick
At /engine/GameTurnBased.lua:51 tick
At /mod/class/Game.lua:1534
---------------- Stack Dump ----------------
--------------- Stack Dump Finished ---------------

This is the latest error I got, but as far as I know it has been exactly the same one every time. By an increasing rate I mean it started out as infrequent as once per around 10 turns and now after traveling a short while I get like 10 of them every time I take a turn on the world map, rendering the game effectively unplayable. I don't run any fan made add-ons.

What I have tried and did not work: Saving and reloading my game after it started happening, going back to some dungeon and then back to world map, going back to Far East.

[Targuil]

Fighting a random orc patrol (the first one I found) managed to fix the problem for now. Errors lingered for a couple of turns after returning to the world map from the patrol fight but quickly stopped.

[cowking]

Had the same problem, went away after completing vor pride.