The kids did some button mashing on the game likely and ended up somehow mapping the firebutton within advmame to bring up the volume control. If you push up or down then, it scrolls through other control options. Push fire again and it goes away. This pretty much makes things unplayable. It's only when a game is running, not in attract mode, so it's mame specific.
What is this hotkey known as so I can look for a menu config that is mapping it to joy button1?
Pic of what comes up is below:
