[liquidbase]

Issue fixed with this function

function ab:FixMBBR()
    for i = 1, 6 do
        local Button = _G['MultiBarBottomRightButton'..i]
 
        Button:SetAttribute('showgrid', 1)
        Button.noGrid = nil
        Button:ShowGrid(ACTION_BUTTON_SHOW_GRID_REASON_CVAR)
        Button:Show()
    end
end

SetAttribute has caused an issue with MultiActionBars.lua from Blizzard. All buttons are set to nil, only buttons 1-6 of the MultiBarBottomRight are set to true. nil or false shows the grid and the button while true hides the button.

In the end, @humfras got me on it. Thanks for that