I believe Pinchaser nailed it:
"It appears to me to be an issue coachJim alluded to... body position at the foul line. It appears that in shot one your foot moves left to right and thereby closer to your target line in your slide. Where as in shot two your slide moves straight.. and there by off balance. I have seen this many times and is usually caused by the fact that while you might actually slide in or very close to the same position, the path to the foul line is different. I would suggest that in shot one you are farther left on the approach than in shot two. I wish I could see the feet work to prove this."
It appears as though you wander further left in the beginning of the approach on the first shot, coming to your target from a different angle - further left on the approach - which is compensated for in your follow through going to the right to hit your mark. On the second approach, where you walk straighter, the mark is more in front of you, appearing slightly to your left, so you compensate in your follow through across your body to hit your mark, losing leverage in the shot.
I'd suggest putting tape markings on the approach, one where each step should land, and on the fronts of your your shoes. Then, point the camera at your feet from the foul line and see what happens. I'm guessing you simply need to plot a straighter/more consistent course at the beginning of your approach.
Good luck with working on your game.
