Error saving Notes and Pages to Files on iPhone 15

I find it handy to write Notes or make quick edits in Pages and save to Files on iPhone.

In Notes it's usually easy to do by setting the Notes option to Send & simply choose Save to Files in the popup list of actions & name the document before saving to Files.

In Pages, simply choose Export from the top right-hand menu & again choose Files on the popup actions menu, again naming the document & saving to Files.

Recently however I get an error message telling me the file can't be saved "either because the file doesn't exist of the folder doesn't exist."

What's the cause? Any tips, tricks, URLs or insights for this strange new issue?

iPhone 15 Pro Max, iOS 17.2.1

Thanks!