Normally you don't even need the Stop triggered audio, because using the Play audio command a second time will automatically stop the first audio clip that was started with the same command. Something is wrong, and I cannot see that in the advanced actions.
Rick describes the alternative which was the only way possible for versions before those two commands. Audio Objects: Control them! - Captivate blog
Just a tip: group those buttons, so that you use one command to hide them .... Captivate 6 - Advanced Actions - Captivate blog