Check body swing matching throughout the stroke. Mike/Armando getting long reach and engaging legs first. Taylor getting good reach but using back to early. Gardner not reaching as much but keeping shoulders level. Also using back too early. Pause the video at several points during the drive to see the difference in angles.

Mark gets good body angle at the pause point but lets the hips slide under the shoulders as he compresses to the catch. As a result, he lacks body angle at the catch and opens the back right away on the drive. Pause the video to see this difference between him and Alex.