[Bug]: module/pulseaudio does not preserve audio balance on volume change

[kdato]

Checklist

• I have read the appropriate section in the contributing guidelines
• I believe this issue is a problem with polybar itself and not a misconfiguration on my part
• I have searched for other open and closed issues that may have already reported this problem
• I have checked the known issues page for this problem.
• I have followed the debugging guide to narrow down the problem to a minimal config.

Steps to reproduce

I have polybar-3.7.1 from here. In my .config/pulse/default.pa I have this line to set the audio balance on my speakers: set-sink-volume 0 +0% +35%.

When I start my DE, polybar loads fine and the default balance if fine. Using the mouse wheel on polybar to change the audio volume changes each audio channel by a different percentage. This does not preserve the audio balance.

Minimal config

[bar/DP-2]
monitor = ${env:MONITOR:DP-2}
background = ${colors.background}
foreground = ${colors.foreground}

modules-right = pulseaudio date

font-0 = Noto Sans Mono:size=11:weight=bold;2
font-1 = unifont:fontformat=truetype:size=8:antialias=false;2
font-2 = siji:pixelsize=10;1
font-3 = Font Awesome 6 Free:style=Solid:pixelsize=11;2

override-redirect = true
cursor-click = pointer
cursor-scroll = ns-resize


[module/pulseaudio]
type = internal/pulseaudio
click-right = pavucontrol
label-muted-foreground = #FFBF00
label-volume-foreground = ${root.foreground}

format-volume = <label-volume> <bar-volume>
label-volume =  %percentage%%
label-muted = "   "

Polybar log

No response

Expected behavior

Using the mouse wheel on polybar to change the volume, both audio channels should change by the same amount to preserve the volume balance.

Actual behavior

When I use the mouse wheel on polybar to change the volume, the right audio channel changes by +5% or -5%. But the left channel changes by only +3% or -3%, which means that module/pulseaudio does not preserve the volume balance.

To confirm, using the volume wheel on my keyboard, or using the mouse wheel directly in pulsemixer, does preserve the balance as expected.

Window Manager and Version

labwc-0.7.1 or enlightenment-0.26.0

Linux Distribution

Slackware-current

Polybar version

polybar-3.7.1

Additional Context / Screenshots

No response