Engraving from dxf's has always been a bit of a 'Lucky Dip' ,especially the early versions
of Inkscape, I noticed that your file and a previous one posted earlier are very small scale
wise, I discovered that if you work with a larger image in Inkscape the trace bitmap works
better, then import it to CB and re-scale it. In the posted file see pic I used a 31x31 icon in the pic,
The original image imported as a dxf is fairly lumpy, whereas the scaled version ran through the file
cleaner 'Inscape prefs' set to output as splines looks better.
There is a plugin 'polyline smooth' which could help here too.
Dave