Vive Focus 3, Unreal Engine, Set Tracking Origin Eye Level; head movement tracking not working

[ForensicDJS]

In my Unreal Engine project (4.27) I am trying to set the player view at a very specific position at the beginning of my VR simulation so am using "Set Tracking Origin Eye Level" option. This puts the player and view right where I need it but there is no tracking of the head movement. Also, the hand tracking is no longer aligned with the HMD. Not sure what I am missing. Note that the position is within a moving, animated actor.

When I use "Floor Level" or "Stage" options, head tracking is fine though the starting position is not ideal, since (I believe) it is based on the custom floor settings set in the play area options. But this doesn't work for my project as it needs to be a sitting-type view.