Change from active to passive (C-API)

[sven1904]

I'm using Bullet's C-API and try to switch from active joint control (in CONTROL_MODE_POSITION_VELOCITY_PD) to passive interaction, i.e. the robot joints shall move to a specific position and after reaching that position, it shall be able to move according to external forces.

Unfortunately, it's not possible to move the robot at all after it already moved actively.
But, if it did not move before, it's able to be pushed by external forces.
What happens when I move the robot actively and how can I revert this?

In the following video, you can see how the robot reacts if it does not move before.

compliant.mp4

And the following is the result after moving the robot first to an initial position.

stiff.mp4

As you can see, it's not possible to 'drag' the robot with the mouse anywhere because some internal controller is preventing any motion.

I already tried to 'disable' all position/velocity controllers and set zero torque for the torque controller via

  for (int i = 0; i < _joint_ids.size(); i++)
  {
    b3GetJointInfo(_physics, _body_id, _joint_ids[i], jointInfo);
    for (int mode : {CONTROL_MODE_VELOCITY, CONTROL_MODE_POSITION_VELOCITY_PD,
                     CONTROL_MODE_PD, CONTROL_MODE_STABLE_PD})
    {
      _command = b3JointControlCommandInit2(_physics, _body_id, mode);
      b3JointControlSetMaximumForce(_command, jointInfo->m_uIndex, 0);
      b3JointControlSetKp(_command, jointInfo->m_uIndex, 0);
      b3JointControlSetKd(_command, jointInfo->m_uIndex, 0);
      b3JointControlSetDamping(_command, jointInfo->m_uIndex, 0);
      _status = b3SubmitClientCommandAndWaitStatus(_physics, _command);
    }
    _command = b3JointControlCommandInit2(_physics, _body_id, CONTROL_MODE_TORQUE);
    b3JointControlSetDesiredForceTorque(_command, jointInfo->m_uIndex, 0);
    _status = b3SubmitClientCommandAndWaitStatus(_physics, _command);
  }

but it did not change anything.

Can anyone tell me how to make the robot 'compliant' again?