Precision in construction of lantern gears

[azalanono]

Hi, looooo,
I wanted to use FreeCAD with your freecad.gears Addon to generate gears for bicycle-chain. Finally I found the right module of m=4.06 so it looked fine.

Now the strange thing, and I have no idea where this comes from:
I had to export this 3D-drawn gear as AutoCAD DXF file for laser cutting. Initially I wanted to directly export as .dwg, but Freecad is unable to do this. I can select Autocad 2D DWG, but no file is generated, Do I tried .dxf.

• The first try pointed out that this was no closed path, so the laser cutter software was not able to add the offset.
• So I had to convert the dxf to AC1009-dxf first (I only have ACAD R14). I used an online converting tool for that. Then I found out that the gear was a mix of splines and arcs, where end points of one and start point of next item did not exactly match. So Autocad refused to join elements to one path.

Where do this deviations come from? Are they caused by FreeCAD's .dxf generating? Or is the precision in your module too low?
Is there any way to fix this?