I would recommend Saving / Exporting the DXF as an older file version.
Most CAD packages will have options for DXF R12 or R14 and these
should give better results with correct circles.
Looking at the Text objects and these appear to be 3D DXF entities,
which results in the facets ( these are the lines inside the font) from
the 3D object being converted to 2D lines. Exporting just the open
fonts from your CAD package should fix this.
I hope this helps and please let me know if you have any further questions