Keyframing on text and graphics not working as expected.

I am using keyframes to move text and graphics across the screen in a simple Premiere Pro CC project, but the movement is not working as I would expect.  There are a total of four keyframes on the video layer that contains the text that I wish to move across the screen.  The first keyframe is setting the starting position off screen, the second keyframe is there to slow down the text movement, the third frame is the end of the slow movement and start of another fast movement that leads to the fourth and final keyframe that again takes it off the screen.  Simple enough.  The problem is between the second and third key frames that I will call the "Center Keyframes".  For about the first half of these "Center Keyframes" everything work as expected but about half the way through, the text starts moving backwards.  If you are watching the X-Position you start off watching the number move in a positive direct, as expected but at the near half-way point, the numbers start moving in a negative direction.  The problem is there is no keyframe to justify that change of direction.  What am I not understanding?