Activating/deactivating languages mix seems to not flush container cache

505 r25290
WAS 6.1
Oracle (db storage)

I have created a site in french, and then added some content, still in french
I have then activated english, and imported a section, defined in english only. So, the title of the home page of this new section is displayed as "N/A" in the top menu (corp V2) in french.
I have then activated language mix, left the admin center, and the page title is still "N/A", whereas it should be the english one, as nothing is defined in french.
I have used /cache/off : this time, I got the good information, that let me think it was just an invalidation problem when we activate/deactivate language mix.
But when I remove /cache/off , the content is still the good one, as if I had used /cache/offonce . I have same issue with /cache/bypass .
So, I don't know if it is just invalidation that is not immediate, or if we have two issues: an invalidation issue when updating language mix option, and an issue with /cache/off and /cache/bypass that updates the cache whereas it shouldn't.