Ibooks not working as expected

Hello,

I ceated epub 3 file.

I have two audio file audio1 and audio2.

When ibooks reads the page1 it uses audio1 file on ipad. Every thing works fine.

When page turns and it starts reading page 2 it should use audio2 file as that is the only file I defined in smil related to page2. When it reads it jumble up audio1 and audio2 words at the same time.

WHAT IS THE BUG ?

I checked my epub is coded correctly.

Please help here if you any clues.