Have you had your borehole water analysed? Even the best glyphosate formulations will do better with water conditioners for anything harder. X Change needs to be added slowly as the tank fills - chucking it in first creates an oily scum in the tank that doesn't go away.We added x-change to our Roundup vista last Autumn as we have hard borehole water and it made it go a bit 'gloopy'(if there is such a word).
Used some later without x change at 1.6l/ha seems to have killed all the weeds.
Was told Vista doesn't need a water conditioner.