The horizontal factor file is an ASCII file with two columns on each line. The first column identifies the horizontal relative moving angle (HRMA) in degrees, and the second, the horizontal factor (HF). Each line specifies a point. Two consecutive points produce a line segment in the HRMA-HF coordinate system. The angles must be input in ascending order. If the HRMAs are not in ascending order, the line segments can cross, resulting in ambiguous HFs.
Make sure the horizontal relative moving angles are sorted in increasing order. The documentation for How PathDistance works gives more information on the formatting of the parameter file.