video ok but no audio in conference system when there are more than 6 people on the vs2017 project

Hi, LibMediasoupClient. Lib is used to develop the Windows conference system. When there are only 3-5 people in the room, everything is ok.But when there are more than 6 people in the room, WebRTC reports an error, as follow:
( Playout error: rendering thread has ended pre-maturely

( Recording error: capturing thread has ended pre-maturely
As a result, video ok but no voice , what’s the problem。can you help me? thanks

We cannot give support about libwebrtc library, sorry.