I discovered that my code was using the screen zoom in one of the DXF export calculations, and that the math used to guess at a good connector radius was not quite right. After fixing those two issues, I also made a change to improve the solid link shapes, and I think that I have it right.
Linkage Solid Link
DXF File Solid Link
The connector size is calculated to be a proportion of the overall mechanism size. That’s very different from the screen image which uses a fixed size for the connectors regardless of the mechanism size. The screen connector size is always the same even when zooming in and out.
Anyhow, there is a new Linkage program available here. This has these DXF export improvements.