I'm using html entities in the quiz definition, e.g. & minus; or & times; etc ... CF7 displays them ok the first time the page is accessed, but when submitting the form, regardless whether it is successful or not, the quiz label is escaped to & amp;minus; and & amp;times; etc.
(I used spaces above because the WP forums are parsing them ...)
As a side note, the & nbsp; that CF7 adds after the label is causing some difficulties when skinning the form to match a custom website design. I suggest removing the & nbsp; and using styles, in particular you can add span.wpcf7-quiz-label { padding-left: 1ex; display-inline-block; } in the stylesheet for the same effect, but which can be easily overriden by the website's stylesheet.