I get this error, just installed the addon.

Date: 2020-01-04 14:08:32
ID: 9
Error occured in: Global
Count: 1
Message: ..\AddOns\Backpack\core\Slots.lua line 143:
attempt to index local 'Slot' (a nil value)
Debug:
[C]: ?
Backpack\core\Slots.lua:143: UpdateSlot()
Backpack\core\Slots.lua:239: UpdateContainerSlots()
Backpack\core\Slots.lua:245: UpdateAllSlots()
Backpack\core\Core.lua:263: Toggle()
Backpack\core\Blizzard.lua:4: ToggleAllBags()
[string "OPENALLBAGS"]:1:
[string "OPENALLBAGS"]:1

I don't play the game any more, so this won't get fixed unless someone provides a patch.

I get the same error I think.

Message: Interface\AddOns\Backpack\core\Slots.lua:143: attempt to index local 'Slot' (a nil value)
Time: Wed Jun 17 17:09:11 2020
Count: 1
Stack: Interface\AddOns\Backpack\core\Slots.lua:143: attempt to index local 'Slot' (a nil value)
[string "=[C]"]: ?
[string "@interface\AddOns\Backpack\core\Slots.lua"]:143: in function UpdateSlot' [string "@Interface\AddOns\Backpack\core\Slots.lua"]:239: in function UpdateContainerSlots'
[string "@interface\AddOns\Backpack\core\Slots.lua"]:245: in function UpdateAllSlots' [string "@Interface\AddOns\Backpack\core\Core.lua"]:263: in function Toggle'
[string "@interface\AddOns\Backpack\core\Blizzard.lua"]:4: in function <Interface\AddOns\Backpack\core\Blizzard.lua:3>
[string "=[C]"]: in function `ToggleAllBags'
[string "OPENALLBAGS"]:1: in function <[string "OPENALLBAGS"]:1>