Ok folks, I've just found a solution for you (and me ^^).
Our problem is that the "zoom" parameter (borders) of stabilization is not applied on export.
So what I've successfully tried is the following:
• Borders set to zoom on your Stabilize behavior;
• Switch to the Properties tab of your "stabilized" track;
• Look for the scale value and remember it;
• Switch back to the Stabilize behavior and set Borders to normal;
• Switch back to the Properties tab, Scale and manually set the previous value;
• Export
• Voilà!
I can not believe Apple released Motion 5 with so much obvious bugs on it. I've been in touch with the support for weeks, about a constant sound export problem (glitch, no-synced, etC.), which looks to be hopefully now corrected thanks to our exchanges. Motion is out for many months now, it's hard to believe how slow they do answer and correct bug. I'll submit the following just in case.