It's hard to guess the cause when I don't know what command you are calling to export.
You could try "Export Project" instead of "Export Chapters", or vice versa.
If you have LibreOffice or OpenOffice, you can use the yWriter import/export extension instead, which will give you an ODT document. In this case you don't need to insert a page break for each scene, but can set each scene to its own page using style sheets.