Need help on Quaternion.lookAt (NaN output)

FishBoneEK

https://doc.qt.io/qt-6/qml-qtquick3d-quaternion.html#lookAt-method

For the following arguments:

Quaternion.lookAt(
  Qt.vector3d(0.47212299704551697, -0.05714830011129379, -0.03842129930853844), 
  Qt.vector3d(0.0174984410405159, -0.1452823281288147, -0.038421452045440674), 
  Qt.vector3d(-0.9816991090774536, -0.19043900072574615, 0), 
  Qt.vector3d(0, 1, 0)
)

The output is a NaN quaternion? What's the issue here?

My understanding is lookAt calculates the rotation of the forwardDirection vector of an obj at sourcePosition to the other obj at targetPosition, so that forward after rotation aligns to target - source, and tries to keep upDirection close to the positive Y axis. Is this correct?