Boxcollider2d sinks into Ground when falling on a non straight surface

Hello, I'm programming an endless runner for android in a blocky graphics style and when my character falls onto a non straight surface it kinda sinks into the Ground. When i then jump, it comes out of the ground but on coming down, it sinks in again, however, it doesnt fall through.

Here are some pictures of the player sticking in the floor:

By Default the player looks like this: