Divi Builder Error When Making Page Updates

Have you tried to enable Safe Mode & see if it works: WP Admin > Divi > Support Center > Safe Mode > Enabled

If still doesn't work, then try the below to troubleshoot the issue:
1. See if the issue happens on all pages or certain page.
2. Create a new page & save it & see if it works.
3. If the issue only occurs on specific page & it works on new page, then most likely there's a coding in the specific page that getting block by the server firewall. To confirm that, in the new page, try to add a code module with this: <style></style><script></script> & save it & see if the error occurs. If it couldn't save with that coding, then you need to check your web host & ask them to check for any server error log that prevent the saving & whitelist the action.