Thanks Harald,
I found a way which works, finally! I am happy to send you a login if you want to see how things are functioning on the site.
Today I edited an article translation that I had not tried yesterday, and it saved without problem.
Hopeful, I opened the article I tried to translate yesterday, and was not able to save the changes on it.
The only difference was that I needed to change the html code, rather than the wsywig text. I have JCE back on again.
I then decided to try using the JCE <> code button icon, instead of of toggling the editor. And this worked!
So the solution is - use the editor icon to edit the code, do not toggle. Then the changes will save.