I tried on my test sites but could not replicate the issue.
Please check the following.
1) Can you confirm that you are fully updated? (Theme and Plugins)
The latest version numbers as of this time are
X 6.4.6, Cornerstone 3.4.6
If you find anything to be out of date, you can review our update guide.
2) Try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
3) Clear plugin cache and browser cache, then temporarily deactivate your cache plugin
4) Temporarily remove custom CSS and JS that you have added.
If none of these helps, kindly provide us your wordpress admin login in Secure Note