I am having the same problem - I have the Sydney Pro theme and I always used visual editor in the SiteOriginEditor. Then just quite suddenly when I went to make some text changes recently, I can no longer use the visual editor option and I also can’t seem to save any new text changes.
I get this message when I try to add new content on any page and save it into the SiteOriginEditor:
“There is a newer version of this widget’s content available.RestoreDismiss
Clicking Restore will replace the current widget contents. You can revert by refreshing the page before updating”
The visual editor option is enabled in my administrator profile and I’ve cleared my browser cache. Also tried disabling all 3rd party plugins and changing my theme, yet still the same problem.
Hopefully you can help