Hello,
thank you for taking the time.
I would like to know how to solve the problem that a GameObject with rigidbody component sinks into a terrain.
I have attached a video 
where you can see my problem.
To move the GameObject I used rigidbody.movePosition()
Of course, I added the colliders to both objects.
Many greetings!
If that’s your collider failing, try setting your RigidBody → Collision Detection to Continuous.