Echo Speaks - Stop Flash Briefing via webCoRE?

I have a webCoRE Piston that has an Echo Flex in my bathroom play music when the light about the shower turn on. It stops playing when the same light turns off. If I play my Flash Briefing instead, it will start playing when the light turns on, but the STOP command that stops the music does not stop the Flash Briefing.

How can I have webCoRE stop a flash briefing playing on an Echo Flex?

THANK YOU! I would have never thought to try that.