Solved Can't Edit DU Headers or Footers without it erasing all content

This is caused by two possible culprit:
1. Wordfence plugin.
2. Your hosting modSecurity.

Let me know if you have Wordfence plugin installed.

 

Can you temporarily try to disable your modSecurity & see if the issue still persist or not.

 

If yes, then you may check out this modSecurity whitelist & see if it works: https://divi.help/threads/your-save-has-failed.7740/#post-25517

Taken from the link:
1. Find whitelist.conf or exclude.conf file under /usr/local/apache/conf/modsec2/ (CentOS in my case, your’s path can be different)
2. Add the following rules: https://gist.github.com/dipakcg/efd64b6a033aad6886f3b3859a6fed2a#file-whitelist-conf-or-exclude-conf

 

It's because for our header & footers, we have inline CSS in code module, thus it's triggering false positive on some firewall. If you add a code module with inline CSS for your normal pages, then you will face the same issue as well.

For that case, try this workaround by removing the inline CSS code module: https://divi.help/threads/cant-edit-custom-menu.4315/#post-14478
**The code module that shown in the video can be found in every custom header & footer styles.
**There might be more than one code module in the custom header & footer styles. If you find other code module, try to go to the settings & copy the CSS code & paste in WP Admin > Divi > Theme Options > Custom CSS & then only remove the code module.
**And to avoid it popping as new tab & wipe out the content, try to edit it in Visual Builder. In Visual Builder, if the issue still persist, you will not be able to save it, but it won’t wipe out your content.

 

What if you try to edit it in Visual Builder & press save & see if there's any server error logged.