Have been having this issue over the past few weeks where clicking the update world quests button would sometimes cause extreme lag that would not go away until game is restarted.

Today I received the same thing along with a lua error (other times it's happened with no error reported).

29x AllTheThings\AllTheThings-1.9.9c.lua:5262: Usage: PlayerHasHeirloom(itemID)
[C]: in function PlayerHasHeirloom' AllTheThings\AllTheThings-1.9.9c.lua:5262: in function <AllTheThings\AllTheThings.lua:5258> AllTheThings\AllTheThings-1.9.9c.lua:7360: in function <AllTheThings\AllTheThings.lua:7311> AllTheThings\AllTheThings-1.9.9c.lua:7393: in function <AllTheThings\AllTheThings.lua:7390> AllTheThings\AllTheThings-1.9.9c.lua:7332: in function <AllTheThings\AllTheThings.lua:7311> AllTheThings\AllTheThings-1.9.9c.lua:7393: in function <AllTheThings\AllTheThings.lua:7390> AllTheThings\AllTheThings-1.9.9c.lua:7332: in function <AllTheThings\AllTheThings.lua:7311> AllTheThings\AllTheThings-1.9.9c.lua:7393: in function <AllTheThings\AllTheThings.lua:7390> AllTheThings\AllTheThings-1.9.9c.lua:7332: in function <AllTheThings\AllTheThings.lua:7311> AllTheThings\AllTheThings-1.9.9c.lua:7393: in function <AllTheThings\AllTheThings.lua:7390> AllTheThings\AllTheThings-1.9.9c.lua:13276: in function Update'
AllTheThings\AllTheThings-1.9.9c.lua:13237: in function `?'
AllTheThings\AllTheThings-1.9.9c.lua:53: in function <AllTheThings\AllTheThings.lua:51>

Locals:
(*temporary) = nil

I believe this was fixed, comment if not.