In all the Years i‘ve been using ts isn‘t happened something like this.
In my private Channel I can hear one mate just with my (left) ear.
In all other Channels we hear him normal.
I tried to localize the problem and I just can say that this is not a client problem.
Everyone who joins this channel is just hearing him in one ear.
This is why.
Your channel uses Opus Music and not Opus Voice as codec. This needs to be changed.
Thanks for your help