Background of the issue:
I was trying to access the WP Menus Sync feature in WPML by opening the URL wp-admin/admin.php?page=sitepress-multilingual-cms%2Fmenu%2Fmenu-sync%2Fmenus-sync.php. I encountered issues while doing so.
Symptoms:
I received a warning message: 'Undefined property: WP_Error::$name' and several warnings about 'Cannot modify header information - headers already sent'. These warnings were related to the file wpml-menu-sync-functionality.class.php on line 158 and functions.php on lines 7168 and 7144.
Welcome to the WPML support forum. Before passing this thread to my colleague, I would like to share some suggestions and possible solutions for the issues you mentioned.
This alert won't affect the normal functioning of WPML. As a temporary workaround, we recommend setting debug mode to false by adding or changing the following code in your wp-config.php file, located at the root of your WordPress installation:
define('WP_DEBUG', false);
This should help to resolve the issue until a permanent solution is implemented in future releases. Please try it after a site backup and let us know your feedback.
