Wwise certification 101 Lesson 3 Sequence container (shells) implementation failure

Question

I have an issue implementing the sequence container in cube.

Everything works fine triggering the Fire_Shotgun_Player event from WWise , however , when I export my sound banks and trigger the event from cube , the shells sequence container seems to be played twice.

Attached  is a capture log for the event.

http://postimg.org/image/hut5gt3xt/

Any suggestions would be very much appreciated

Thanks in advance 

seb