During Screen Capture w/ window, Sound does not hear from Mac's speaker.

At first, During Screen Capture w/ window, Sound was hear from Mac's speaker.
but after I did screen capture around 45 minus, Sound become broken. and finally, it stop.
once I stop the screen capture and restart again. but Sound does not come from Mac's speaker.
Option is seated Audio Source : Computer, Delay, none.
Recoded movie has Sound. no problem.

Tech data ID :346639874