[Justin Ledoux]

The problem is very easy to solve, but very well hidden.

In the timeline, select the item you are animating. Go to the inspector, open up the transform box, and select the rectangle with little dots at each 4 corners (free transform button). When you select that you will see the path that your item is following. If you click on that path ( so in the canvas ), and then right click it, you will see a menu that lets you choose from linear or smooth. Select linear for all the keyframes on that path and your problem is solved.

Cheers!