There's not much to see regarding screenshots for the dialog. I push the button on the controller to advance the dialog to the next bit and at the end of the other rock talking I am inside the dialog again immediately.
Actually, come to think of it... when I approach the dialog starts automatically without me having to open the conversation. I'd think that's the actual issue...
As for the audio-level slider, you would have to keep its setting somewhere in a global variable and when the dialog is opened initialize it with the saved value. Or maybe you could have it check the audio player what volume level is set.