I'm trying to resolve this issue where some pages can't create a specific langauge.
I can only find reference to bug 26280, but not sure if it's the actual cause. Most pages are working as expected, but in one section, and any nodes below it I can't create all the languages, but can create most of them.
I would search the site some more, but the bug searcher is rubbish, and just returns all results no matter what keywords I search for.
Sounds like bug #26280, there is a hotfix available that you can try out if you register a support case.