Our site is doing the same too.
Infact whilst trying to make a minor text change, it lost the whole page structure and now it wont allow us to rebuild the page back to its original form. As clicking ‘update’ shows random results. We’re currently left with half of the web page on display. No matter what we do, it wont save the extra information and on occasions it deletes the whole page again and we have to start again.
Its pretty frustrating as we dare not touch the rest of the site which is built using ACF.
The only option is to restore the whole site, unless someone knows how to restore a single page from a previous backup??
I have also submitted our issue on the contact page.
