I am having a problem while moving the viewport of random jumps to different levels of zoom. My screen capture of the problem is here: https://www.dropbox.com/s/0835tj399mxlhj9/WHY!!!.mov. This happens while I use option and the left mouse button to move around the canvas, and is seemingly unpredictable. Sometimes it will jump to a level of zoom where I can no longer see the part of the model where I am working and I have to hit F to reframe before recomposing to continue work. If anyone has a solution, thanks in advance.
-Tim