Return to base layer - showing blank

I have set up four audio files that first two are set on triggers to the relevant layer. The third one set to come back to the base layer.

The fourth audio continues to plays seamlessly , however all the graphics and text on the page are blank (not appearing). They are set to always show and the show buttons are active. Strangely what does still appear is the header text on the templated header top, and bottom templated bar.

I cannot figure out why the other graphics are not showing on the return to the slide.