Half of the document is seen as changed after pasting some text

Hi all!
I’m in the process of editing a book. I’m working on a quite big (about 2.5 MB) .rtf file with lots of comments and change tracking enabled, Windows 7x64, libre office Yesterday I had to paste some text from older file to the file in question. I did, and proceeded with editing, nothing bad or weird happened then. Unfortunately, today when I opened the file, the whole text from the place where I pasted to the end of the file is seen as changed. When I open the file in Open Office, it’s not an issue, but unfotunately Open Office doesn’t see comments in .rtf files, as you probably know.
Is there anything I can do about that?
PS: sorry for my English, it’s not my native tounge :wink: