Unnormalized quaternions cause corrupted tracking

[rfn123]

Hi, first of all thank you for your work!

I am using your ROS package on Ubuntu 16.04 with ROS and an Intel Realsense R200 camera. The format of the depth image is similar to that of the Kinect.
After starting the particle tracker and initializing the objects position, Rviz throws a warning like this:

[ WARN] [1560802095.431834161]: Interactive marker '0' contains unnormalized quaternions. This warning will only be output once but may be true for others; enable DEBUG messages for ros.rviz.quaternions to see more details.

Furthermore,
rostopic echo /particle_tracker/object_model
is completely empty.

What exactly causes this? And is there a way to e.g. tune the parameters to lower the chance of this happening?

Thanks!