I'm ~30 minutes before starting a game and am noticing this happening on both Chrome and Firefox. I have Dynamic Lighting and FOW activated. Panning the map in any direction reveals the entire map for about 1 second before the darkness renders over it. This occurs whether panning using the scroll bars, by holding and dragging with right-mouse, or by using the "pan map" tool. Of particular concern, the darkness does not render and appropriately cover the map until the panning motion stops, meaning players could potentially slowly pan around a map and see its full structure and contents. Sorry if the cause is slightly different from the origin of this post (i.e. ctrl - / + reveals the map), but the results are the same - players can see an entire map when the view changes.