Why terrain shadows are gone when using a few more point lights in the scene?

In Terrain settings I've created the lightmap using calculate lightmap button and have already checked the shadow checkbox and defined my directional light in its settings. BUT when I add bunch of point lights to the scene all the tree shadows on the terrain vanish I only get the shadows of a building and other 3d objects. What is goin on? thanks,

You probably just have to re-calculate the lightmap after you add lights to your scene.