When docked, laptop switches to HDMI/Display port, instead of headphones. Headset microphone not available. [20BXCTO1WW, Realtek ALC3232]

[Christopher Barrington-Leigh]

When my laptop is docked, I used to use a headset plugged into the dock for meetings. Both microphone and audio out were connected to my headset.

Since the last update, my sound does not work like it used it, and I cannot make it work like I want.

In particular, whenever I dock:

 - the output device changes to "HDMI/DisplayPort 2 - Built-in Audio". I do not know what that is (nothing is connected to HDMI), but it results in strange audio behaviour in which I can hear something through headphones but it's faint and does not respond to volume control.
 - audio input switches to internal microphone. Worse, there is no longer the choice to use the headset microphone, which is mandatory for those in my meeting not to hear my keyboard taps.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: alsa-base 1.0.25+dfsg-0ubuntu5
ProcVersionSignature: Ubuntu 5.3.0-24.26-generic 5.3.10
Uname: Linux 5.3.0-24-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC2: cpbl 3431 F.... pulseaudio
 /dev/snd/pcmC2D0c: cpbl 3431 F...m pulseaudio
 /dev/snd/controlC1: cpbl 3431 F.... pulseaudio
 /dev/snd/controlC0: cpbl 3431 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Mon Jan 6 06:36:12 2020
EcryptfsInUse: Yes
InstallationDate: Installed on 2019-01-24 (346 days ago)
InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.3)
PackageArchitecture: all
SourcePackage: alsa-driver
Symptom: audio
Symptom_Card: Built-in Audio - HDA Intel PCH
Symptom_Jack: Black Headphone Out, Right
Symptom_PulseAudioLog:

Symptom_Type: Sound works for a while, then breaks
Title: [20BXCTO1WW, Realtek ALC3232, Black Headphone Out, Right] fails after a while
UpgradeStatus: Upgraded to eoan on 2019-10-31 (66 days ago)
dmi.bios.date: 09/13/2017
dmi.bios.vendor: LENOVO
dmi.bios.version: JBET66WW (1.30 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20BXCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: SDK0J40697 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvrJBET66WW(1.30):bd09/13/2017:svnLENOVO:pn20BXCTO1WW:pvrThinkPadT450s:rvnLENOVO:rn20BXCTO1WW:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad T450s
dmi.product.name: 20BXCTO1WW
dmi.product.sku: LENOVO_MT_20BX_BU_Think_FM_ThinkPad T450s
dmi.product.version: ThinkPad T450s
dmi.sys.vendor: LENOVO

[Christopher Barrington-Leigh (cpbl)]

This is not just a problem when I dock. In fact, even when I correct the problem by selecting the correct output device in sound settings, it reverts after a while back to the incorrect one (HDMI/Display port)