FolkeW on "[Plugin: YITH WooCommerce Wishlist] Shared link gives 404 error"

Well title actually says it all. When I (or a customer) tries to share a wishlist via the buttons every thing goes well but the link posted does return a 404 when clicked. The link created looks like this: http://www.playmoparts.nl/wishlist/&user_id=1. The shop is closed at the moment, so testing from outside is difficult. What can be wrong?

http://wordpress.org/plugins/yith-woocommerce-wishlist/