Nobody has a clue? I guess it's a bug then. I can't believe nobody ever uses multiple text variables in the same paragraph.
On the forums, please allow more than one day to give you a response to your question. It was posted on a Sunday, and if other posters are anything like me, they're usually well away from this page on a Sunday.
That said, I do use more than one text variable in a line, but admit that I have never then relied on the same lines to be included into a table of contents. I can tell you that text variables (including live captions) have limitations, such as not fitting over two lines unless they are converted to static text (InDesign Help | Text variables - under the heading "insert text variables" in a "note" at the end of the paragraph).
However, I can confirm that I have tried to replicate your fault and indeed, am getting the same thing here. I'd report it as a bug if I were you: Adobe - Feature Request/Bug Report Form
I submitted a bug report now.
If more people could verify this bug and also submit one, it would really help to press this issue.