My robots, imported using com.unity.robotics.urdf-importer, behave as if a buoy on water instead of being on solid ground. Only the legs/extremities float, and the central sections behave as I want them to

I use ArticulationBody for the elements, and their settings look like this, but for reliability the relevant ones are recreated here (values marked * have undergone several changes in hope of fixing):

• Use Gravity: Yes
• Linear Damping: 0*
• Angular Damping: 10*
• Joint Friction: 10*
• Collision Detection: Continuous Spectulative*
• Articulation Joint Type: Revolute
• Motion: Limited
• XDrive:
  • Lower Limit: -60
  • Upper Limit: 60
  • Stiffness: 100000*
  • Damping: 100Æ
  • Force Limit: 3.402824e+38*

See this this youtube upload for a visual demonstration of the issue

I have tried adding new box colliders to all elements, it didn’t do anything.
Applying a custom physic material can change the friction and bounciness of the central section only, but the extremities continue to ignore anything I do to them