Hi,
I am sorry. I forgot I have some gallery plugins installed and that Quick Edit isn't standard WP option in Media Gallery.
So it's probably issue with Shiba Media Gallery. Plugin is probably not prepared for working with PolyLang - this can be reason why issue happened 3rd time during "classic" editing of media posts.
I am sorry for reporting false issue.
Anyway, Is there way how to reconnect posts?
Thanks,
Tomáš