Problem with ethan prefab.

I am sure you have worked out a solution by now. However here is mine for anyone that is stuck on the same issue:

Edit Standard Assets\Characters\ThirdPersonCharacter\Scripts\ThirdPersonCharacter.cs

Add a call to a new method checkClimb() in public void Move(Vector3 move, bool crouch, bool jump):

     ...
     else
     {
         HandleAirborneMovement();
     }

     checkClimb(); // <-- add this

     ScaleCapsuleForCrouching(crouch);
     ...

Then create a method to handle vertical translations based on a ray check that happens from above in front of the character as they move:

         /// <summary>
         /// Work out Y Movement. We may need multiple checks here later too, to prevent us falling into small cracks.
         /// </summary>
         /// <param name="move"></param>
         private void checkClimb()
         {
             float distanceDown = m_offsetVerticalForVerticalChecks + 2.5f;
 
             //float stepOffsetVerticalForHorizontalChecks = 0.1f;
             //float maxOffsetVerticalForHorizontalChecks = 1.5f;
 
             RaycastHit hitInfo;
 #if UNITY_EDITOR
             // helper to visualise the climb check ray in the scene view
             Debug.DrawLine(
                 transform.position + (Vector3.up * m_offsetVerticalForVerticalChecks) + (this.m_ForwardAmount * this.transform.forward * 0.5f), 
                 transform.position + (Vector3.up * m_offsetVerticalForVerticalChecks) + (this.m_ForwardAmount * this.transform.forward * 0.5f) + (Vector3.up * (m_offsetVerticalForVerticalChecks - distanceDown)));
 #endif
             // Actually do the check
             bool collided = Physics.Raycast(
                 transform.position + (Vector3.up * m_offsetVerticalForVerticalChecks) + (this.m_ForwardAmount * this.transform.forward * 0.5f),
                 Vector3.down,
                 out hitInfo,
                 distanceDown);
 
             if (collided && m_offsetVerticalForVerticalChecks + m_maxVerticalFall > hitInfo.distance)
             {
                 if ((m_offsetVerticalForVerticalChecks - hitInfo.distance <= m_maxVerticalClimb) && (m_offsetVerticalForVerticalChecks - hitInfo.distance > 0.0f))
                 {
                     this.transform.Translate(new Vector3(0.0f, m_offsetVerticalForVerticalChecks - hitInfo.distance, 0.0f));
                 }
             }
         }