Because the skin separator line between the masonry block and the brick is set to a thin pen.
In case of this Composite the skin separator line on the other side of the masonry block is also the contour of the whole composite, therefore it is set to a thick pen, because you want the contours to be thick.
So basically the skin separator line on one side of your masonry skin is set to a thick pen, on the other side of it it is set to a thin pen.
As I wrote earlier, the whole length of the skin separator line will be drawn with the same pen. Since that problematic skin separator line reaches into the body of the wall it joins the problem appears.
So it is no like that you define the contour pen and that contour will be drawn around the adjoining wall bodies. ArchiCAD always takes the individual skin separator lines and draws them one by one. The contour is handled the same way.
About your other issue: can you show me a screnshot of that?
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