I'm on the AT&T version also and had this problem since day one.
I'm using this now: http://goo.gl/uXbGzz
and the problem is still there.
However, playing with the phone tonight, I found a way to zoom while recording that seems to work all the time. While recording, pinch in, as if you're zooming out. A slider will appear at the bottom (or, in the side of you're holding it landscape). You have to use the slider to zoom in and out - just the slider - and every single time i used the slider, the camera zoomed in or out.
Update: And while playing with the camera more, I found that once you zoom in and the slider disappears, you're stuck at that zoom level until you stop recording. Trying to get the slider to reappear means you have to pinch - and if you pinch, then the app crashes.
Update 2: As long as you leave your finger on the slider, you can zoom in or out the whole time.