If you play the animation on 0.1 speed you can see a lot of weird shaking going on during the middle frames. The center point of the drill part is not centered properly so thats why its also moving but you can clearly see the shaking.
If anyone could help clear up what causes this that would be great. I dont know how i stopped the lower part from shaking so much as it had the same problem earlier. I use Maya for the animation if it helps.
The model in question is: