Hi Scott,
Please follow the steps below: (I know you mentioned some steps already but I urge you to do the duplicate steps anyway)
- Ensure everything is up to date according to our version compatibility list here. Please follow the best practices when updating your theme and plugins. Click here for more information.
- Test for a plugin conflict. You can do this by deactivating all third-party plugins, and see 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.
- Remove custom CSS and Javascript from the options and/or Child Theme and test the case.
- If you’re using a CDN, please clear the CDN’s cache and disable optimization services.
- Increase the PHP Memory Limit of your server. Click here for more detailed information and how to increase the PHP memory limit.
- Make sure that you have the version 4.9.6 of the WordPress, if not please backup the website and update to that version.
- Check the Cornerstone with another browser or machine.
kindly get back to us with the result of the steps above and URL/User/Pass of your WordPress dashboard using the Secure Note functionality of the post to follow up the case if you still have problems.
Thank you.