If you referring to theme module translations, there is a known bug.
I've committed a fix for that, but its only partial fix.
https://github.com/thirtybees/thirtybees/pull/958/commits/64f4bb9a238c08dd77252bc009ce37a5c0ff6124
Whats actually happening now is that the page shows the theme modules translations but when saving it saves it to the default theme instead.
If you are referring to other type of translation (not modules) than please explain exactly whats your issue with