Quiz Timer

Hi everyone, 

Could someone please help checking about the errors in this slide 2.3 with the JavaScript timer?

When the player click "finish" and the Score is less than 15, the failed layer appears. But when user click retry button and jump back to the base layer to retake the quiz, the timer did not reset and there will be 2 timers running? 

Please help me as I try so many options to fix it but it is not working! Thank you so much