Physics messed up with cardboard scene

I am in the process of putting together an app using the Google Cardboard SDK. The user will be able to use the app with or without cardboard. So, there is a switch button inside the app, that activates and deactivates stereo rendering. The app also uses the Vuforia SDK to track image targets. If a specific target is recognized, some 3D objects above the target and a particle system starts to emit particles.
Everything works fine in non-stereo mode. Particles are emitted and falling...

Physics messed up with cardboard scene