sts-settings-update-{$sectionid}

/**
* Filter, if errors occured during update.
*
* With this filter you can hook into the settings update process
* and perform the update.
*
* The filter name is 'sts-settings-update-{$sectionid}’
*
* If an error occurs, return a WP ERROR object, which describes the problem.
* Otherwise return true
*
* @since 1.0.0
*
* @param (boolean)     true             No error
* @return (mixed)         $return         true or WP Error
*/

With this filter you can basically hook into the settings update process. Each tab creates its own filter. So, for example for the Email tab the update process would be sts-settings-update-email. The $sectionid corresponds with the ID of a settings tab. More information can be found in the filter sts-settings-content.

The filter needs to return true, if no error occured or a WP Error Object describing the error.