The slide turns white when I go back and stop audio

Hello,
I've created a project with these features:
the slides advance automatically;
when revisiting "resume saved state";
all the slides have a new level with an audio and this part automatically when the slide appears;
all the slides are connected to the master;
in the master I inserted the "forward" and "backward" custom buttons.

Problem:
When the second slider goes back to the first slide, the first slide slides without playing the audio and the buttons do nothing anymore.
The only one that works is the "back" button but when I click it it becomes the white page.

help please