(using version 18.1.0.1)
I'm still getting this LUA error (#491) when opening a profession window.
Today I got it by opening JC crafting orders, doing nothing, then going to the Scribes' table and upon opening Inscription skill window, I got this error:

65x Auctionator/Source/API/Internal.lua:2: Contact the maintainer of CraftSim to resolve this problem. Details: Usage Auctionator.API.v1.GetVendorPriceByItemLink(string, string)
[string "=[C]"]: in function error' [string "@Auctionator/Source/API/Internal.lua"]:2: in function ComposeError'
[string "@Auctionator/Source/API/v1/GetVendorPrice.lua"]:18: in function GetVendorPriceByItemLink' [string "@CraftSim/Pricing/PriceAPIs.lua"]:214: in function GetMinBuyoutByItemLink'
[string "@CraftSim/Pricing/PriceSource.lua"]:103: in function GetMinBuyoutByItemLink' [string "@CraftSim/Classes/PriceData.lua"]:145: in function Update'
[string "@CraftSim/Classes/RecipeData.lua"]:252: in function new' [string "@CraftSim/Libs/classic.lua"]:64: in function RecipeData'
[string "@CraftSim/Init/Init.lua"]:528: in function TriggerModulesByRecipeType' [string "@CraftSim/Init/Init.lua"]:85: in function <CraftSim/Init/Init.lua:83> [string "@CraftSim/Libs/GUTIL/GUTIL.lua"]:564: in function checkCondition'
[string "@CraftSim/Libs/GUTIL/GUTIL.lua"]:570: in function WaitFor' ... [string "@Blizzard_SharedXML/Shared/Scroll/ScrollUtil.lua"]:490: in function SelectElementDataByPredicate'
[string "@Blizzard_ProfessionsTemplates/Blizzard_ProfessionsRecipeList.lua"]:159: in function SelectRecipe' [string "@Blizzard_Professions/Blizzard_ProfessionsCrafting.lua"]:887: in function Init'
[string "@Blizzard_Professions/Blizzard_ProfessionsCrafting.lua"]:358: in function <...lizzard_Professions/Blizzard_ProfessionsCrafting.lua:357>
[string "=[C]"]: ?
[string "@Blizzard_SharedXMLBase/CallbackRegistry.lua"]:144: in function <...eBlizzard_SharedXMLBase/CallbackRegistry.lua:143>
[string "=[C]"]: ?
[string "@Blizzard_SharedXMLBase/CallbackRegistry.lua"]:147: in function TriggerEvent' [string "@Blizzard_Professions/Blizzard_ProfessionsFrame.lua"]:207: in function SetProfessionInfo'
[string "@Blizzard_Professions/Blizzard_ProfessionsFrame.lua"]:139: in function <...s/Blizzard_Professions/Blizzard_ProfessionsFrame.lua:102>

Locals:
(*temporary) = "Contact the maintainer of CraftSim to resolve this problem. Details: Usage Auctionator.API.v1.GetVendorPriceByItemLink(string, string)"

I'm also getting the following LUA error when first opening Alchemy window near a lab bench:

2x ...rfaceCraftSim/Classes/SalvageReagentSlot.lua:32: Error CraftSim.SalvageReagentSlot: Trying to set item which is not in possible salvage item list
[string "=[C]"]: in function error' [string "@CraftSim/Classes/SalvageReagentSlot.lua"]:32: in function SetItem'
[string "@CraftSim/Classes/RecipeData.lua"]:366: in function SetAllReagentsBySchematicForm' [string "@CraftSim/Init/Init.lua"]:576: in function TriggerModulesByRecipeType'
[string "@CraftSim/Init/Init.lua"]:85: in function <CraftSim/Init/Init.lua:83>
[string "@CraftSim/Libs/GUTIL/GUTIL.lua"]:606: in function checkCondition' [string "@CraftSim/Libs/GUTIL/GUTIL.lua"]:612: in function WaitFor'
[string "@CraftSim/Init/Init.lua"]:74: in function TriggerModuleUpdate' [string "@CraftSim/Init/Init.lua"]:126: in function <CraftSim/Init/Init.lua:106> [string "=[C]"]: ? [string "=[C]"]: in function Init'
[string "@Blizzard_ProfessionsTemplates/Blizzard_ProfessionsRecipeSchematicForm.lua"]:192: in function <...emplates/Blizzard_ProfessionsRecipeSchematicForm.lua:186>
...
[string "@Blizzard_FrameXML/Mainline/SecureTemplates.lua"]:667: in function <...ddOns/Blizzard_FrameXML/Mainline/SecureTemplates.lua:649>
[string "@Blizzard_FrameXML/Mainline/SecureTemplates.lua"]:681: in function <...ddOns/Blizzard_FrameXML/Mainline/SecureTemplates.lua:674>
[string "@Blizzard_FrameXML/Mainline/SecureTemplates.lua"]:723: in function `SecureActionButton_OnClick'
[string "@Blizzard_ActionBar/Mainline/ActionButton.lua"]:1438: in function <Blizzard_ActionBar/Mainline/ActionButton.lua:1408>
[string "=[C]"]: ?
[string "=[C]"]: ?
[string "@Blizzard_FrameXML/SecureHandlers.lua"]:266: in function <Blizzard_FrameXML/SecureHandlers.lua:263>
[string "=[C]"]: ?
[string "@Blizzard_FrameXML/SecureHandlers.lua"]:296: in function <Blizzard_FrameXML/SecureHandlers.lua:279>
[string "=(tail call)"]: ?

Locals:
(*temporary) = "Error CraftSim.SalvageReagentSlot: Trying to set item which is not in possible salvage item list"

First recipe in the window is: Transmute: Meat to Pet

And I have done Auctionator search for everything, including the above and this one.

And I just got the same error (the original I have reported) when opening LW window. I opened Skinning about 15 minutes earlier but killed a lot of things inbetween and teleported too. It also defaults to an old world recipe.

on what recipe did the error occur?

This particular case was Inscription which opens with Fae Revel Masque (because it's the first in the order of favorited recipes), but it also occurs with Enchanting followed by Tailoring (Tailoring window opens with Cindercloth Cloak for the same reason).

are those current or old world recipes?

try a full scan with auctionator and then open again
for me its working fine

Old world recipes.
This doesn't seem to happen when you open only that one skill, at least I used to get it when I open one and then the other.

Got the same error when opening JC window that doesn't even have any favorites so it opens at Algari Crushing.

#619