Oculus and Unity: grab object makes avatar fall through the floor? - unity3d

Question

I just downloaded the basic Oculus sample framework for Unity (I'm on 2018.2) and am trying to combine the TeleportAvatar and AvatarWithGrab scenes - to have a teleporting avatar able to grab objects.
All is well - I dragged an object with OVR Grabbable script (below) into the teleport scene, added OVRGrabbers to the avatar object and hit play. I can successfully pick up the object after teleporting, etc but for some reason after interacting with grabbable object a while my character falls through floor (maybe teleports below floor?).
I even added a new floor to be sure there was a box collider to prevent falling; however, this had no effect.
I looked for any overlap between the controls and even turning off teleport, but the grabbable object script is causing the fall. Why is this?
Doing the grabbing motion with right hand (teleporting hand) doesn't cause any issues if I'm not near a grab object.
/// <summary>
/// An object that can be grabbed and thrown by OVRGrabber.
/// </summary>
public class OVRGrabbable : MonoBehaviour
{
[SerializeField]
protected bool m_allowOffhandGrab = true;
[SerializeField]
protected bool m_snapPosition = false;
[SerializeField]
protected bool m_snapOrientation = false;
[SerializeField]
protected Transform m_snapOffset;
[SerializeField]
protected Collider[] m_grabPoints = null;
protected bool m_grabbedKinematic = false;
protected Collider m_grabbedCollider = null;
protected OVRGrabber m_grabbedBy = null;
/// <summary>
/// If true, the object can currently be grabbed.
/// </summary>
public bool allowOffhandGrab
{
get { return m_allowOffhandGrab; }
}
/// <summary>
/// If true, the object is currently grabbed.
/// </summary>
public bool isGrabbed
{
get { return m_grabbedBy != null; }
}
/// <summary>
/// If true, the object's position will snap to match snapOffset when grabbed.
/// </summary>
public bool snapPosition
{
get { return m_snapPosition; }
}
/// <summary>
/// If true, the object's orientation will snap to match snapOffset when grabbed.
/// </summary>
public bool snapOrientation
{
get { return m_snapOrientation; }
}
/// <summary>
/// An offset relative to the OVRGrabber where this object can snap when grabbed.
/// </summary>
public Transform snapOffset
{
get { return m_snapOffset; }
}
/// <summary>
/// Returns the OVRGrabber currently grabbing this object.
/// </summary>
public OVRGrabber grabbedBy
{
get { return m_grabbedBy; }
}
/// <summary>
/// The transform at which this object was grabbed.
/// </summary>
public Transform grabbedTransform
{
get { return m_grabbedCollider.transform; }
}
/// <summary>
/// The Rigidbody of the collider that was used to grab this object.
/// </summary>
public Rigidbody grabbedRigidbody
{
get { return m_grabbedCollider.attachedRigidbody; }
}
/// <summary>
/// The contact point(s) where the object was grabbed.
/// </summary>
public Collider[] grabPoints
{
get { return m_grabPoints; }
}
/// <summary>
/// Notifies the object that it has been grabbed.
/// </summary>
virtual public void GrabBegin(OVRGrabber hand, Collider grabPoint)
{
m_grabbedBy = hand;
m_grabbedCollider = grabPoint;
gameObject.GetComponent<Rigidbody>().isKinematic = true;
}
/// <summary>
/// Notifies the object that it has been released.
/// </summary>
virtual public void GrabEnd(Vector3 linearVelocity, Vector3 angularVelocity)
{
Rigidbody rb = gameObject.GetComponent<Rigidbody>();
rb.isKinematic = m_grabbedKinematic;
rb.velocity = linearVelocity;
rb.angularVelocity = angularVelocity;
m_grabbedBy = null;
m_grabbedCollider = null;
}
void Awake()
{
if (m_grabPoints.Length == 0)
{
// Get the collider from the grabbable
Collider collider = this.GetComponent<Collider>();
if (collider == null)
{
throw new ArgumentException("Grabbables cannot have zero grab points and no collider -- please add a grab point or collider.");
}
// Create a default grab point
m_grabPoints = new Collider[1] { collider };
}
}
protected virtual void Start()
{
m_grabbedKinematic = GetComponent<Rigidbody>().isKinematic;
}
void OnDestroy()
{
if (m_grabbedBy != null)
{
// Notify the hand to release destroyed grabbables
m_grabbedBy.ForceRelease(this);
}
}
}