play once feature>the player goes back and forth

[Livyatan]

i am working on a project that has very simple cues:
i play a clip (mic dv) in the play once feature.
many times when the "needle" finishes to play the clip, in the end instead of stayin in the end of the clip it goes a little bit back and forth,
in this project this is a serious problem
please help
do you know what to do to prevent this from hapenning?
Livyatan.com