Adding page in Dynamic form

I have three pages form and added one "Add" button on Page2. And, I am using the following script in click event:

_Page2.occur.max="4";
_Page2.addInstance(1);

When you click the add button, it actually adds the pages to the file. But, once you save and reopen it the file, it only shows 3 pages. All the pages you added did not show.

Does any one know why?