ARKit error after changing robot.usdz color

I'm trying to change the color of the robot.usdz supplied in the

https://developer.apple.com/documentation/arkit/capturing_body_motion_in_3d 

sample project.

When I run the default project, it works fine. However, if I select part of the robot model in Xcode and change the color using the Material Inspector, I then get these errors:
  • 1. Created entity character does not contain supplied joint name: lefttoesjoint.

  • Cannot get joint count for non-character entity.

  • Unable to load model: The operation couldn’t be completed.

I'm not sure is there a step I'm missing in changing the color, or whether there's something else going on?

ARKit error after changing robot.usdz color
 
 
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