Hi Mike,
Yes, we’ll need to get your login credentials. For the meantime, please try deleting each element one by one while testing the SAVE functionality (make sure you have a backup). Usually, the cause of this issue is the type of content being added. Example, prohibited iframe, for data payload that contains forbidden characters, or there is an internal error.
If it’s due to internal server error, then please edit your site’s wp-config.php and replace this line define('WP_DEBUG', false); with these new lines.
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);
Then test the saving functionality again, then download the file /wp-content/debug.log through FTP and provide its content through a secure note. Or if you can upload the file to any file sharing site then just provide the download URL in a secure note.
Thanks!