Landscape artifacts


I created a nice 4k terrain in World Machine 2 and exported it to UE4. I set it size like mentioned here: with maximum height of 3072m (in WM). After loading my terrain in engine, it looks very nice and detailed from distance, but from close view I got some strange artifacts(?) on edges, like here:

I got this same with other terrains. I’ve also tried to scale down to 2k my terrain, but there is no difference. That’s how it look from distance:

I have no idea what is wrong.