Hey Thomas,
Thanks for the additional info. Cornerstone working in his iPad and the slug conflict are significant clues. I have tested Weglot also though and I could not replicate the issue. I’m not sure why he would copy when it’s not necessary. I tried renaming both Page Title and Slug too and the page is still editable in Cornerstone.
Since it works in his iPad, the problem could be in his browser. Please advise him to clear the browser’s cache and if he has browser extensions, they need to be temporarily deactivated for testing. Also test in other browsers including incognito mode in his PC.
Regarding the slug conflict, I’m not sure why his page was duplicating but it’s certainly not an issue with Cornerstone nor Weglot. If he has a page duplicator plugin, that could be the cause. The duplicate will not work because Cornerstone data is tied to the original page only.
If he’s using the duplicated page as a template, he should use the Template Manager instead.
Is the “options page x/#/options
not working” also connected to Weglot conflict in his site? Please tell him to reset his htaccess file by renaming it to .htaccess-bak. Then in WP Admin Menu, go to Settings > Permalinks and just click the Save Changes button. If this does not work, please advise him to open a thread here and give his WordPress Admin and FTP credentials in a Secure Note and also post the URL of this thread for reference.
Thanks.