To reproduce:
1. Open attached project
2. Select the sprite "terrainas" and add it to the scene
3. Attach a Rect Transform to the sprite
4. Scale it - make the whole thing smaller
5. Attach a box collider2d
6. Enter play mode, inspect that the collider is in a bad position (you might need to deselect/reselect the gameobject)

Seems to be an issue with scaled rect transforms. Reopening the project somehow solved the problem for existing sprites.