Map I am in reloads

At random times the map I am in will stop responding for a couple of seconds, then the loading screen gears will appear for a couple seconds. Following that, the map puts me back to where I was standing however the fog of war has returned to the explored parts of the map. I can see all the check points I have visited and can teleport to them, however I then have to go back and reveal all the areas I have already explored.