I was one of the main drivers for ensuring that the cautionary note for Gold in excess of 5 microinches was flagged.  If you are getting such high variability, I suggest doing two things then re-measuring. 
1) Are the pads being measured at least 60mils x 60 mils (1.5mm x 1.5mm)?  If not, the values may be off due to additional e saturation coming from the wrapped edges.
2) is your aperture sized smaller than the pads be measured?  If not, select an aperture size smaller than the pad being measured.