TikZ transparency group breaks with overlay

I was trying to implement this solution to draw a transparent arrow using a scope with transparency group. It works fine.

Unfortunately my picture needs to be overlayed on some text. When adding the overlay option to my tikzpicture environment, the scope‘s content simply disappears.

Is there any hope to get that working?

From left to right: no overlay (works), remember picture with overlay (doesn’t work) on a square, remember picture without overlay (works).

documentclass[margin=.5cm]{standalone}
usepackage{tikz}

begin{document}

begin{tikzpicture}
    draw (-1,-1) rectangle (1,1);
    fill[blue] circle (1);
    begin{scope}[transparency group, opacity=.5]
        fill[red] (.5,.5) circle (.5);
        fill[red] (-.3,-.3) circle (.7);
    end{scope}
end{tikzpicture}

begin{tikzpicture}[remember picture]
    coordinate (z) at (0,0);
    draw (-1,-1) rectangle (1,1);
end{tikzpicture}

begin{tikzpicture}[remember picture, overlay]
    fill[blue] (z) circle (1);
    begin{scope}[transparency group, opacity=.5]
        fill[red] (z) ++(.5,.5) circle (.5);
        fill[red] (z) ++(-.3,-.3) circle (.7);
end{scope}
end{tikzpicture}

begin{tikzpicture}[remember picture]
    fill[blue] (z) circle (1);
    begin{scope}[transparency group, opacity=.5]
        fill[red] (z) ++(.5,.5) circle (.5);
        fill[red] (z) ++(-.3,-.3) circle (.7);
end{scope}
end{tikzpicture}

end{document}

documentclass[margin=.5cm]{standalone}
usepackage{tikz}

begin{document}

begin{tikzpicture}
    draw (-1,-1) rectangle (1,1);
    fill[blue] circle (1);
    begin{scope}[transparency group, opacity=.5]
        fill[red] (.5,.5) circle (.5);
        fill[red] (-.3,-.3) circle (.7);
    end{scope}
end{tikzpicture}

begin{tikzpicture}[remember picture]
    coordinate (z) at (0,0);
    draw (-1,-1) rectangle (1,1);
end{tikzpicture}

begin{tikzpicture}[remember picture, overlay]
    fill[blue] (z) circle (1);
    node[overlay] at (z)
     { begin{tikzpicture}
       begin{scope}[transparency group, opacity=.5]
        fill[red] (z) ++(.5,.5) circle (.5);
        fill[red] (z) ++(-.3,-.3) circle (.7);
       end{scope}
       end{tikzpicture}};

end{tikzpicture}

begin{tikzpicture}[remember picture]
    fill[blue] (z) circle (1);
    begin{scope}[transparency group, opacity=.5]
        fill[red] (z) ++(.5,.5) circle (.5);
        fill[red] (z) ++(-.3,-.3) circle (.7);
end{scope}
end{tikzpicture}

end{document}