Comment 9 for bug 418505

If I open your SVG with Inkscape r22179 and repeat the same steps with the first two arc segments (scale ~ 200% uniformly, then drag start / end nodes) - I get perfect circles in both cases.

But I do see the difference in the rendering of your SVG in Firefox and Batik (compared to Inkscape): the arc seems like squeezed a little bit and its stroke is not uniformly of the same width. Could it be that the transformation matrix isn't correct after the scaling, but only on certain platforms/architectures?