Hi Sutriano,
Thanks for writing in! Could you please try creating a new email form, add it into a test page and check your issue again.
Also make sure that you’re using the latest version of X theme and plugins by following our version information guide here (https://theme.co/apex/forum/t/troubleshooting-version-compatibility/195) and update any outdated plugins (https://theme.co/apex/forum/t/setup-updating-your-themes-and-plugins/62).
Also I see that you’re using a caching plugin, so I would suggest you to disable your caching plugin temporarily and test your issue further.
If you’re still having issues, try testing for a plugin conflict by disabling your other 3rd party plugins except Cornerstone plugin. If the issue is resolved, then you can activate your plugins one by one to see which plugin causing this issue.
Let us know how it goes.
Thanks!