I too am getting this error, and another related one I think. When I click "Duplicate Page", the new page created is always totally blank, no matter what I try. And sometimes when I try and delete the unwanted blank pages, I am getting the same error as the OP, confirmation message never disappears, and the page does not actually delete from the Page Toolbar. .....Now my game is littered with useless unwanted blank pages, and I can't easily make a copy of a page that I want to alter. Very disruptive to GM prep! I have just submitted request [#79658]