Lost audio during playback on UDP network stream (VLC v3.0.12 on Window64)

hi all: Found a problem with VLC media player(VLC v3.0.12 on Window64) when it to play multicast medias. I use UDP(legecy) with VLC to broadcast videos for about 5 hours video on LAN, and use the same version to receive videos on other Win64 Devices. It went well in the begining until about 1 hour when the client vlc lost sound(audio). The video went ok but the auido piece. I had to use the menu on the vlc client： Media=>Open Recent Media=> XXX, XXX standards for short cut of the network stream, to restart the receive of the stream. The Sound will come back to normal until about 1 hour later it disappear again. The sympton sometime occurs or not , especially for the second 1 hour slot.

I feel there must be a bug in the audio process part of the software for multi-cast. Need help to sort it our since I am using it for broadcast and receive townhall videos.

Thanks