Landscape looks unsmoothed, with dynamic directional light shadows

Hello everyone! I have a question for you. Is this bug, or it’s just me cannot understand something? Here is the trouble:

I am using dynamic day/night cycle in my game, so the sun is movable light source, with dynamic shadows. And this causing very uncomfortable visual effects on the terrain. It looks like landscape is without smoothing, and i can see actual faces. It’s hard to explain, but you can see this on the screenshot below.

I think, this is a bug, because my friend faces with the same trouble, and we cannot solve it.

I have same issue with landscape that i’ve created in World Machine.
4036x4036 resolution, 62x62 segments