Collisions arc rotate cameras and terrain

Hello, I have a followed problem. My camera collides correctly with the terrain, only from the bottom of the terrain (bottom side of mesh). Problem is, that from above the camera passes through the terrain down. How to turn this math?

One of the possible answers - you have inverted normals in your model.
For more exact answer one would need more info from you. Playground example also could help to solve the problem more quickly.