Was using adi, switched over to betterbags. Unable to open bank or if I switch to list instead of grid. This error will not resolve even with a reload. It just keeps repeating and prevents the bank from opening.

73x BetterBags/data/equipmentsets.lua:31: bad argument #1 to 'pairs' (table expected, got nil)
[string "=[C]"]: in function pairs' [string "@BetterBags/data/equipmentsets.lua"]:31: in function Update'
[string "@BetterBags/data/items.lua"]:116: in function RefreshBank' [string "@BetterBags/frames/bag.lua"]:168: in function Refresh'
[string "@BetterBags/frames/bagslots.lua"]:111: in function <BetterBags/frames/bagslots.lua:107>
[string "=[C]"]: ?

Locals:
(*temporary) = nil
(*temporary) = "table expected, got nil"
= defined =[C]:-1

Agreed. I am on retail version of game. The issue is that the sets variable on line 27 is nil so when attempting to cycle through pairs , the table is empty. I can work around with a nil check something like
if sets ~= nil then return end

but that is likely not the ideal solution.

Probably a good idea to say which version of the game you are playing. Someone on discord had a similar problem earlier, which turned out to be caused by leatrix messing with things in classic wow.

I am trying to figure out how this happened in the first place -- this technically shouldn't ever happen, and I can't reproduce it. I'll add a guard regardless, but I have no idea why the API is returning invalid data here.