How to update the nav mesh destination to a random point?

I have an enemy ai which update it's destination to the player when it sees it (enter chase state). But after it gets to a reasonable distance to the player I want to override this destination to a random one so it doesn't stand still in front of thr player. How to do so, I have tried a lot but the ai just freezes in its place and every frame a new point point is generated. I want it to br updated after the ai reaches it first.