Pages is not saving my document changes

This is very strange. I'm a long time Apple user and I've never seen anything like this.

The problem happens on all my documents, however for an example I have a monthly report that I write.

From January 2022 through to September 2024 everything is working fine. I duplicate the document, rename it, and then open it, make my changes, command S and then close it and shutdown Pages. I'm not relying any autosave options. The iCloud sync

For the last 4 months I've been doing exactly the same procedure but my edits are not saved. When I look at those documents now they all show the September 2024 data. I've lost 4 months of reports - not happy.

Here is August 2024 (on the first of the month I write the report for the previous month):

And then September 2024:

But the October 2024 report looks like "September 2024"

So, maybe I made a mistake and forgot to update the title...

Let's check November 2024:

It is still the same - another lost month.

December 2024?

So maybe I made a mistake once, but not three times.

This is now officially bad!

When I open these documents I get a popup that doesn't really make any logical sense:

So, a notice to upgrade, but I'm not doing that now (see below).

Similarly, I'm not collaborating so I'm not going to iCloud, I click the "OK" button and carry on. It's a local document on my MBP and I'm using a local Pages app on my MBP, everything is local. I don't need the cloud to do anything with this document.

And please don't tell me to restart my computer, that is the sort of thing you tell Windows users, not OSX users.

And don't tell me to upgrade. I'm a LAMP developer and upgrading takes me a week to rebuild my environment. That's a week I don't have time for.

Does anybody have a real solution to this?