Nexus 4 wireless charger slipping off?

Just an hour back got my "orb" charger, 2 of them (I have 2 Nexus 4). With lot of excitement I placed the phone onto the orb surface, in 10 mins I found the phone lying on the phone. Tried both the phones, both the chargers. The orb surface just doesn't hold the phone, it SLIPS OFF.

Check this video. http://www.youtube.com/watch?v=DKTORRMeoxE (Posted by another person).

As I searched forums I found many people saying their orb has a magnetic surface it is too tightly held, but for sure mine doesn't have any magnetic hold. It is just working on silicon friction. Anybody has more info on this? Does your orb has any magnetic hold? I would hate to return this back to Google. But it looks completely unusable.