Thanks for the video. I see that a link from ‘Add New’ (page) button has additional parameter ‘lang’: post-new.php?post_type=page&lang=de
I have to block any link different from not selected at menu items list – some link to the same page just with different parameters may lead to another menu item. That’s why such problem appears from time to time.
I will add exclusion for the ‘lang’ parameter used at post_new.php page.