[Resike]

Don't get the hassle about this, i can freely move/scale/parent/show/hide/setwidth/setheight the frame even in combat, without getting any taints. The key object here is the SetUserPlaced(true)

local moving
hooksecurefunc(ObjectiveTrackerFrame, "SetPoint", function(self)
    if moving then
        return
    end
    moving = true
    self:SetMovable(true)
    self:SetUserPlaced(true)
    self:ClearAllPoints()
    self:SetPoint("CENTER", UIParent, "CENTER", 0, 0)
    self:SetScale(1.1)
    self:SetWidth(300)
    self:SetHeight(400)
    self:SetParent(TargetFrame) -- Only for default Blizzard unitframes.
    self:SetMovable(false)
    moving = nil
end)

Of course i did'nt tested with all of the quest items, but i guess if one is working properly then all should.

Two things could cause this taint issues, if you have an addon which abuses this frame badly, or if you have ANY ADDON which calls ObjectiveTracker_Update() at any point. If you call ObjectiveTracker_Update() at any point by an addon then you are fucked.