Pages and Numbers docs will not save on my MacBook Pro running Sonoma

Sonoma 14.5 on MacBook Pro

We can talk Numbers, or Pages, they both seem to do the same thing.

After several of these unexplained issues, I have narrowed down the problem

1 - open an existing, locked, document. Unlock and make changes, use cmd-S to save your work (old habit) - behaves normally.

2 - leave the document open for 'some time' - quite a long time, go for a walk, do some thinking. Return.

3- make more changes. use cmd-S again and document returns error 'cannot autosave, you do not have permissions'

4 - a spotlight search reveals many, say 30 instances of the document. (pages)

workaround - make duplicate works, so increment version number within nomenclature and complete the task

4- look for reports, and find previous issues around use of Google drive etc.

This is a new MacBook Pro. These documents are by default using iCloud, so only Apple tech is involved.

Does anyone have a more detailed explanation - and a solution?

[Re-Titled by Moderator]