PDF output problem for a very specific case of shading

MdC code like
m##//

won't render correctly in PDF output, with "gray" shading (you should get a shaded owl, and you get a gray square).

This code is made with a owl sign, with a shading sign from the "shading symbol" menu over it.

The problem is that in the PDF output, I avoid transparency (for preserving CMYK colours), and the gray square is drawn over the owl.

Note that the other shading systems, quadrant based or sign based, don't have this problem.

I will fix this problem when possible.

Temporary Workaround

Solved in version 5.7 for free groups, which were the actual problem pointed out to me: shading is always placed below the rest (forgot to test it for m##//).

A possible solution is to draw the shading first, like this : //##m, or to use other kinds of shadings (the quadrant shading and the "sign" menu shading work fine).