Comment by aisamu

I "fixed" this with a Hammerspoon snippet that monitors input changes and reverts them:

    mic = hs.audiodevice.findInputByName("MacBook Pro Microphone")
    function handle_deselected(_, type)
      if (type == "gone") then
        if not mic:inUse() then
          mic:setDefaultInputDevice()
        end
      end
    end
    mic:watcherCallback(handle_deselected)
    mic:watcherStart()