I've noticed this as well in Virtual Villagers. I had a new child born as Guapi, same as his father, but after changing their names to Guapi I and Guapi II, I've had no trouble. For a while, Guapi I had weird actions under his name.
While examining the cactus he said he was "trying to move the boulder." Later, while examining the same cactus, he was "drinking from the well." I think I dragged him about and that straightened him out.