It has something to do with $clang. Sometimes, but inconsistently, a handful of the prompts change to English, even if I'm logged in with my user language set to Vietnamese looking at a Vietnamese-only survey.

In particular, the prompt I think is "Question:", but I think the survey and the groups still have their proper prompt. I'm thinking that if you hit activate from there you have the chance of it publishing without the survey question fields.

At a minimum, the create should fail in this case, since it's worse the create a bad table than to throw an error message.

Please attach a sample survey showing this behavior so that we can try to reproduce the problem.

The export / re-import of the Vietnamese survey causes utf8 problems, I've submitted that as another bug.

But please look at that section of code in common_functions -- there's a definite problem with the language is looking for questions with lang_code as 'en', when it should always be looking for base language questions.

Importing the survey attached at http://bugs.limesurvey.org/view.php?id=5834 I can't reproduce the problem. The SGQA columns for the two questions of that survey are created.
Tacman: Does the problem with the missing columns maybe only show up when creating a new survey instead of importing the Vietnamese one?

I can reproduce this - just activated the Hội thảo ở HCM -Minh survey and it didn't have any SGQA columns generated (so perhaps the fix to the other problems broke this).

Fixed with patch https://github.com/LimeSurvey/LimeSurvey/commit/96c94379f1c9fd6a814bcf4a176d66017b6f242c

1.92RC5 release