Thanks Torsten. We were on WordPress 6.5.4 so I updated to 6.5.5, reActivated Real Cookie Banner and the problem has gone away!! When it wasn’t working we didn’t get any error messages to the screen – it just wouldn’t save changes to Pages. All the Plugins we use were on their latest versions.
I will try (in a day or so as bit busy…) to see if I can track down any error logs.