After Effects Text Tracking Issue – Center Letter Not Moving When Increasing Tracking

This behaviour is determined by the number of characters in a line of text - i.e. text with an odd number of characters vs. text with an even number of characters. There are 17 total characters (including spaces) in the text from your attached video, "I DON’T WANT THIS". This is an odd number, and any line of text with an odd number of characters must have one character in the middle that represents the "halfway point" of that line of text. Whenever you see a center-locked character during Tracking it just means you have an odd number of characters. When you don't see a center locked character, you have an even number of characters. 

Think of the word "EVEN":

• 4 letters. 2 letters on the left of center EV, 2 letters on the right of center EN
• There is no actual character that represents the "halway point" of the word. The halfway point is the space between EV and EN. This center point is still being locked in place, we just can't see it because it's empty space.

Now think of the word "ODD":

• 3 letters. 1 letter left of center O, 1 letter right of center D, 1 letter is the true center D.
• In this case, the halfway point is now an actual visible character instead of just being some empty space between characters.  The same thing is happening either way - characters spreading equal amounts on each side of a locked center point. The only difference is whether or not the center point is itself a visible character, or if it is the empty/invisible space between two characters.

There are a couple workarounds for "unlocking" the center character when using a Tracking animator on a line of text with an odd number of characters.

1. Including/Excluding Spaces (only applicable if there is more than one word in the line of text):

In the case of  "I DON’T WANT THIS", there are only 17 characters if we include spaces in our character count. If we choose not to count spaces, then we get an even number of 14 characters. So, let's tell the Animator to exclude spaces. Go to Animator>Range Selector>Advanced and find the option called Based On. This is set to Characters by default, which really means Characters Including Spaces. But, if we switch it to Characters Excluding Spaces, voila, we now see every character move when we increase the tracking because when spaces are excluded, no character is the exact center. 

2. Offset:

Under Animator 1 (or whichever Animator contains Tracking) > Range Selector, if you set the Offset to 1% instead of 0%, you ever so slightly shift the "center" of the Tracking animator. As a result, the character that was previously locked in place is no longer the exact "center" point of the Tracking, so it is now free to move away from the new center position defined by the Offset.

NOTE: Only use option 2. if  1. doesn't work. Changing Offset means you now have one more character on one side of center than the other side, so the text layer will no longer be perfectly centered. This isn't very noticebale unless you really crank the Tracking Amount, but still good to be aware that this method is a passable "cheat", not a perfect solution.