[NationOfJoe]

i thought that as well on first watch, the bag seems to jump or suddenly change.

I think, after watching it frame by frame, the bad is being quickly grabbed by the "hands" and over (what looks like, to my untrained eye) 2 frames the bag gets squashed a little.

i think the hand motion is hidden by the arm, the bag is being held in a slightly weird way which makes it change shape unexpectedly and the hand closes very fast (hard?) making the shape change quickly.

[jcims]

Yeah the hand/pincers clamp down really quickly, deforming the top of the bag and pulling that yellow panel up, exposing a feature at the bottom of the bag that wasn't there before.

The throw just looks like the bag has all of the weight in the bottom.

[squarefoot]

What looks even stranger to me is the way the bag spins when it's tossed over the scaffolding, even more noticeable in the making of video. It may just be an irregular distribution of the weights inside, still it looks odd.