Iphone 5 Fisheye Lens Moving Around?

I bought an IPhone Fisheye for IPhone 5, it's one of those magnetic ones that attach to a magnetic ring around the camera.
Whenever I film videos with it on, when I watch the videos back, it looks like the fisheye is completely moving around the camera as if someone is holding it in place with their hands.
I even took a video while looking at the fisheye to see if it was moving cos maybe the magnet was inneffective but no, that's dead still and when I'm actually recording, it doesn't move around, only after i finish filming i notice this happening.
This didn't happen on iphone 4 why is it happening and how do I stop it?

To stop it, buy a digital camcorder.