So the way I enventually resolved this (still not sure what was causing it), was the basic approach of uploading the current version of the document to the same SharePoint folder as the original version, but with a different filename.
Then deleting the original version & renaming the current version to the original name. After doing this, I was able to ...
Is version control enabled on library? Do you have ability in SharePoint interface to check-out, publish this document?
If yes, you probably need to check-out file in SharePoint, then update it the way you want, then check-in and publish. This way you should get the same version in all applications.
I'm not sure I fully understand the issue you are facing, it does sound like something odd is happening. Are you using web parts somewhere on the page where you are opening the document from? Try going to the actual source document, where it is saved to - then try to open from there.
Also check the Document Library Settings > Advanced Settings.
Follow below steps:
Go to Site Pages library.
Select the ellipses( three vertical dots ) next to your page.
Select Version history.
By default Version history is enabled on Site Pages library. Make sure it is still enabled on it.
To View/Restore/Delete Page from Version history:
Hover on the Modified field and click on the small drop-down arrow inside it....
It is the expected behavior for “Append Changes to Existing Text” feature.
This feature is only available for Multiple lines of text column and is only responsible for values of this column.
If you want to remove all data of this version, select item and click ITEMS > Version History > menu of the specific version > Delete. It will remove the entry of the ...
I could reproduce the issue you are facing. It is default SharePoint behavior. When you delete a version, the value from append only column gets deleted but the values of the other columns are updated to the values in the current active version and the entries that these columns are updated with current values is added to the latest version of that item.