Weird shadows on terrain, keeps disappearing and appearing according to camera's position and angle

I created a neighbor terrain and then when I was moving around in the scene then I noticed there was a big weird circle like shadow on the neighbor terrain. It disappears when I disable the shadows option on the directional light. And when I go near the terrain the shadow disappears, like it is really weird, it keeps popping up and goes away at some angles. This is really annoying please help. This shadow does not appear on any other game object like if I place a plane or a cube on the place of the shadow, the shadow is not being cast on that. And when I disable one terrain the shadow disappears.

Here are the images - https://imgur.com/qCPJCFM ; https://imgur.com/RH2kgbg