Zack, thanks for a quick reply. WMPL does exactly what you wrote above, it allows to blog in several languages.
In admin part, it shows all posts in default language. To switch to another language it adds new GET parameter &lang=
So when I am at calendar and choose to display all langiages, URL shows like this
https://a32.me/wp-admin/edit.php?page=cal&lang=all
but calendar makes internal AJAX request to the server for calendar data and does not include “lang” variable to that request.
in my patch I modified AJAX url to include that variable as well.
I do not think that many users has such plugin combination ?? but if it looks good for you, you can include this fix