What I see is
When you drop the first two boxes, the drop of point is higher than the other boxes , so you actually "drop" the boxes (I like that) and then when you retreat the robot is perfectible normal
When you place the second set, you do the same after the boxes dropped and the tool now is empty, the robot goes down and compresses the boxes, then it goes up
I wonder if that weird motion on the robot is just the tool "going back to normal" after being under pressure