All three axes are actually starting at the same time. What you are most likely seeing is because of different gearing ratios. Depending on the pulley configuration used on the slider, the gear ratio changes, so when the slider starts with the pan, the slider physically moves quicker off the start, because of the gear ratio. 5 inches of travel of the slider does not seem right though, it should be just a very little jump at the start, if it happens.
If having a little movement at the direction change is not acceptable, then we have our Parallax unit for our sliders, that can be used with the 1-axis Second Shooter slider motor, as the auto panning is mechanical, based off the movement of the slider.
If it is more than just a small movement sometimes at direction change, please contact our support team to review with you, if you have not already.
Also, in the future, if you have any problems at all, please contact our support team directly. You can open a support ticket here: http://www.kesslercrane.com/support or send an e-mail to firstname.lastname@example.org. Thanks!