When I dowloand Movies & TV shows in Apple TV on MacOS Catalina I get sound problems?

I download movies on my Mac Mini because I have Viasat satellite reception. The speed is too low most of the month to stream anything, especially HD movies. The problem I'm having now I didn't have in the beginning when I first started using Apple TV in Catalina. I have a Denon Receiver to playback in theater Dolby mode that works well. Once in a while the downloaded movie won't play sound even though all the settings in sound are correct? My question is why?

Mac Min (late 2012) i7 processor, 16GB RAM. Movies played from 12TB external USB drive where library is located.