You may want to create a copy or take a backup of your Thrive website's HTML source.
Unfortunately, there is no way to easily backup the source HTML of each page within the Thrive platform itself. You could get the source for each feature by clicking on each section to activate it and then clicking on the little blue '</>' icon to the left. This will provide the HTML content for that feature.
Another way would be to visit the pages in the web browser ie. <yourdomainname>.com, <yourdomainname>.com/page1, etc., and then press Ctrl+U. This will give you the source HTML for the whole page including the Thrive framework.
Important: Before making any edits to Thrive pages, please ensure that you are only working within one window and that all other Thrive windows or browser tabs have been closed. This drastically reduces the chances of conflicting edits. Another possible source of having issues can be the Grammarly extension if you are a user of this. Make sure that the extension has been disabled before attempting any page edits.
You can access the web pages of a business by following the instructions in the article: Editing a Page with Thrive