[RC-Monster Mike]

It is quite hard to see in the video, but it is easy to hear the slippage. Something is very wrong to have this much slip. Scuffing the slipper rings(particularly the one engaging the slipper pads) is important not only for traction, but also because there is a greasy residue on the rings from the manufacturing process.
Also, what grease did you use to grease the adjustment ring threads? I have found that AE black grease works the best - this is also a very important step, as dry or improperly greased threads will not allow you to fully compress the springs (they don't need to be fully compressed usually to work, but they must be compressed a bit to apply enough pressure on the slipper assembly). With the appropriate grease, you should be able to flatten the springs with fairly light pressure.
Aside from that, the only other cause of excess slip(assuming proper assembly) would be oil or grease somewhere on the slip surface(pads or ring). Can you post a couple still pictures of the assembled diff?