When a hero visits an Oasis, he gets some additional movement points, but all the other Oasis on the map are considered visited by this hero.
It would be better so that each Oasis to be considered independent, so the hero can visit the Oasis located at position 30-35, to get some additional movement points, moves to another Oasis located at position 40-45 and gets some additional movement points.
Change for the same behavior for Watering Hole and Stables.