closed caption do not work in quiz slides

Hello !

In a quiz slide, a voice explain the purpose of an exercice. It begins in the first image of the slide. The audio is an audio slide, not a event one.

There is closed caption for this voice, in the audio, creating with the closed caption editor of the audio sound in Captivate.

But the closed caption refuse to appear in quiz slide in html 5 view. If I click on the button CC, it appears less than 1 second, then desappears again.

(At the end, the project will be a SCORM module, and I already turn it into a SCORM in the project information)
The CC work everywhere else in the rest module for audio, as for video, excepting in quiz slides.

Is there something I did'nt do/check ?

Thanks by advance.