Comment 15 for bug 1409520

Using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit on Win7 SP1 64 bit, I'm affected by this bug, too.
I find it rather annoying, because I often draw diagrams with boxes that fall into the affected width range.

I've played around bit and noticed that the problem seems to appear only within a certain line width range. Here are the instructions for reproduction:

1) Start Inkscape.
2) Draw a rectangle. (A small one for better visibility of the problem.)
3) Set the join to "Round join" in the "Fill and Stroke" panel.
4) Set the stroke width to 1px. The result is step4.png. The upper left corner has no rounded join.
5) Decrease the stroke width. When reaching 0.442px (didn't test more decimals), the join is suddenly correct, see step5.png.
6) Increasing the width produces, again, the wrong result. When 2.581px are reached, the result is correct again, see step6.png.

So at least for me and this testcase, the problem appears for 0.442px <= width < 2.581px.