‘Show only specific number of questions ‘ affects audio player display

When activating the option to ‘Show only specific number of questions’ for a quiz, the audio player display changes.
I have a quiz that uses audio files for the questions. I insert the audio using the [audio] shortcode.

e.g.

[audio mp3="https://example.com/wp-content/uploads/2017/03/audiofile.mp3"][/audio]

I can customise the appearance of the audio player using css e.g.

.mejs-container {
border-radius: 12px;
background: #ffa502!important;
}

But if I activate ‘Show only specific number of questions’ then the audio player changes to the browser default and the css has no effect.