Pages not saving changes in Copied Files

I have a document in Pages I use as a template. I copied the file and renamed it. I then made changes in the new file. I hit save (CMD+S) and sometimes it offers to save it as a new document so I either renamed it or used the name I had originally put in after copying the file.

When I reopen the document, all changes have reverted to the original copied document. Nothing I have done appears in the new document with a new name. I have managed once to save as a new document with "2" at the end and that worked, but mostly, the changes are gone.

I think what is happening is that the original document has some sort of iCloud override that decides my changes are lame and goes back to the original copied version.

What is happening here? I could just use a new document in Pages, but why is a separate document going back to an older version? I have never encountered this on Google Docs or Microsoft and it seems... unintuitive. I know, I know, I should just have a template saved, but why burn hours of my work to teach me this lesson?