pulse audio update broke sound output

[Bret Busby]

Hello.

I am running Linux Mint 21.3 , which runs on the base system of Ubuntu 
22.04.x, which had a recent pulse-audio update, and I have consequently 
lost a channel of sound through the headphones.

I have tried two different sets of headphones, and, with both, a channel 
of sound is now missing; when the output is switched completely to the 
particular channel, no output occurs.

I am wondering whether anyone else has encountered this, and, how to fix 
what the update has apparently done.

....
Bret Busby
Armadale
Western Australia
(UTC+0800)
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