[kurapica.igas]

Well, you can't call the GenerateUnitFrames during combat, the GenerateUnitFrames is used to replace the "refreshUnitChange" to "_onattributechanged", here is a simple version

local _Task = {}
 
grpHeader:SetScript("OnUpdate", function(self, elapsed)
    if not InCombatLockdown() and #_Task > 0 then
        for _, cnt in ipairs(_Task) do
            GenerateUnitFrames(self, count)
        end
        wipe(_Task)
    end
end)
 
function grpHeader:UpdateUnitCount(count)
    tinsert(_Task, count)
end

If you don't create buttons based on the auto-generated unit buttons, the refreshUnitChange and _onattributechanged will do the same work, only the refreshUnitChange won't be fired when a unit is set to nil, so I replace it with a better one when out of combat.