Indeed, problem lies in condlines values that are not rounded properly. The algorithm to get proper values for cones is
sine(angle) rounded to 4 decimal places, multiplied by radius. This is done properly for quads, but condlines use sine(angle) multiplied by radius, rounded to 4dp. The rounding scheme may seem weird at first sight, but it ensures a perfect match with edges/discs that have a unit size, are rounded to 4dp and scaled to size when used.
sine(angle) rounded to 4 decimal places, multiplied by radius. This is done properly for quads, but condlines use sine(angle) multiplied by radius, rounded to 4dp. The rounding scheme may seem weird at first sight, but it ensures a perfect match with edges/discs that have a unit size, are rounded to 4dp and scaled to size when used.