troubble with sound disapearing while c

[mariaan]

I am touring with a band and the keybordist have a Virus kb on stage. we have a problem when changing program in the keybord. when he change sound, sometimes it just disapear and goes silent. he have to restart the keyboard to get the sound back. some days it works fine and other days he have to restart the keybord 10 times during a consert because it goes silent.
could it be a software problem? could it help to update the software or does it sound like a hardware problem?

thankful if anyone have a tip

Maria