Switches microhpones randomly after upgrade to 20.04

I have upgraded ubuntu from the last 18.04 LTS distribution to the 20.04.1 LTS.

After that, pulseaudio randomly switches the input devices, sometimes it cause to freeze my OS for some seconds. In my notebook, I only have one real input device (the internal mic), but also appear a second analoge input (not present in the same notebook using the 18.04 version)

I’ve commented the line load-module module-switch-on-port-available in the file“`etc/pulse/default.pa“, but the problem remains.

Also, I’ve turn off the second device using pavucontrol, but the problem ramains.

The only temporary fix I’ve found is keeping the pavucontrol windows open. In that case, pulseaudio stops switching the devices.

Any help would be very appreciated