I have created 4 pages. All have the same heated Menu and footer, middle pages are populated but some its content of page 2 is showing on Page 1 and 5.
Preview on the left side show the pages as they should but center preview and export show the duplicated content.
It’s not entirely clear what is happening in your project, but this sounds like a dreaded bug from th past that we all hoped was long, long gone. I would suggest sending the project file, along with a bug report.