X Axis assembly does not have same number of gears on both sides?

I started noticing that my printer always prints a few Z-levels, and then it skips to the left a little bit and continues. If the print is tall, this happens several times. I was reading on the forums that there are two different types of gears – 17 teeth and 18 teeth. http://forums.mbot3d.com/uploads/default/84/f7cc99d22fbe4ae7.pdf

It looks like my printer’s X-axis assembly has a 17-tooth gear on one side, and an 18-tooth gear on the other! Has anyone had this problem and can confirm it? I may need to buy a new gear.