[Kanegasi]

DuffedUI replaces OpenAllBagsMatchingContext with an empty function, but the Blizzard UI expects a number returned from that function.

Here's the function called when you open the Soulbind UI:

function SoulbindViewerMixin:OnShow() -- line 85
    FrameUtil.RegisterFrameForEvents(self, SoulbindViewerEvents);
 
    self:UpdateButtons();
 
    PlaySound(SOUNDKIT.SOULBINDS_OPEN_UI);
    
    self:UpdateBackgrounds();
 
    if C_Soulbinds.CanModifySoulbind() then
        ItemButtonUtil.OpenAndFilterBags(self); -- line 95
    end
 
    self:CheckTutorials();
end

Here's what that function calls to open bags:

function ItemButtonUtil.OpenAndFilterBags(frame) -- line 62
    ItemButtonUtil.TriggerEvent(ItemButtonUtil.Event.ItemContextChanged);
 
    local openedCount = OpenAllBagsMatchingContext(frame); -- line 65
    frame.closeBagsOnHide = openedCount > 0; -- line 66
end

When OpenAllBagsMatchingContext is called, it goes through the bags and counts which ones are opening:

function OpenAllBagsMatchingContext(frame)
    local count = 0;
    for i = 0, NUM_BAG_FRAMES do
        if ItemButtonUtil.GetItemContextMatchResultForContainer(i) == ItemButtonUtil.ItemContextMatchResult.Match then
            if not IsBagOpen(i) then
                OpenBag(i);
                count = count + 1;
            end
        end
    end
 
    if frame and not FRAME_THAT_OPENED_BAGS then
        FRAME_THAT_OPENED_BAGS = frame:GetName();
    end
 
    return count;
end

The source of the issue is the very last line of the code you linked:

OpenAllBagsMatchingContext = D['Noop']

Based on common code practices, D['Noop'] should be equal to function()end.

This error can be fixed by changing that line to the following:

OpenAllBagsMatchingContext = function() return 0 end