Scale 9 not scaling correctly?

I’m baffled at this point. I need help.

I have a slider I’ve built. The slider has a special ‘highlight’ on it that expands as the selection expands. It’s SUPPOSED to reach all the way to the slider, but it doesn’t. And I can’t figure out why. When I poll the code, it says that the highlight is the exact width it should be. But visually, it’s 20 pixels off. Wtf.

As you can see by the picture, the gap gets worse as the highlight gets wider. I’ve also included the highlight symbol, as well as the scale9 grid I’m using. The highlight, as you can see in the screenshot, is a Flash vector. There’s nothing else in the symbol beyond what’s in the screenshot.

It’s like there’s some additional stuff in the symbol that Flash thinks it needs to scale somehow. I have no idea why it’s doing this. Anyone?