Panoramic Sun Roof Wind Deflector - how do they work?

After noticing quite some wind noise when driving with the roof open, I found out my Yeti has a wind deflector on it. However, it seems to not be fully working - as it doesn't open or stay up after opening the sunroof. I guess some spring is not loaded, broken or missing. Does someone know how this is supposed to work, and which part I'm missing (or can add to it to make it work)?  By hand I can open it, but then it also doesn't stay open - there is no pressure to really bring it up. 

Thanks!