Hello!
I have attached a screen shot.
As you can see, the main language (Начальный язык) of survey is Estonian (et), all invitations were send in Estonian using Estonian link to the survey. But if a respondent change the language to Russian (ru) on the first welcome screen, Token and E-mail information is not saved (first and second name was not available) in the responses table and also in the token table is not seen, if the respondent has fill in the survey.
If a respondent continue using Estonian language, everything is working correctly.
I'm not sure, that it is a bug, may be there are any options, which I haven't turned on, but I didn't have such situations earlier.