I was also thinking muted tracks at first, but then the text would have not shown up in the preview monitor either. Are your text objects standard Magix 'titles' or are you overlaying still images or something else?
Thank you guys for your quick interest in my case - I burnt many DVDs checking all the options you mention and the result was the same. But I finally got the solution. The very last step in the process of burning a DVD is a box with some options to check out - I picked the "Encode all" one and text was included in the final movie. (I'm not sure if that's the way to solve the case but for me it worked out.)