What happened?

The volume slider and speaker/mute icon shown in the main slice audio bar (Screenshot 1) only function correctly when PC Audio is selected. When the audio output is set to Line Out or Headphone (Screenshot 2), the same slider and mute icon have no effect on the radio's audio output.
By contrast, the dedicated Radio Audio Outputs sliders and Mute buttons in the radio settings menu (Screenshot 3) work correctly for Line Out and Headphone in all cases.

What did you expect?

Expected behaviour:
The main UI volume slider and mute icon should control the active audio output identically regardless of whether PC Audio, Line Out, or Headphone is selected.

Actual behaviour:
The controls only affect PC Audio. Line Out and Headphone output levels are unaffected by the main UI controls; they can only be adjusted via the Radio Audio Outputs settings panel.
Screenshots:

Steps to reproduce

Steps to reproduce:

Select a slice and set the audio output to Line Out (or Headphone).
Adjust the volume slider in the main slice audio bar.
Observe that the radio's audio level does not change.
Click the speaker/mute icon in the same bar.
Observe that the audio is not muted.
Open the Radio Settings > Radio Audio Outputs panel.
Adjust the Line Out slider or click Mute — these work as expected.

Main slice audio bar (PC Audio mode) — controls work here
Main slice audio bar (Line Out / External mode) — controls do not work
Radio Audio Outputs settings panel — controls work for all outputs

Radio model & firmware

FLEX6400 4.1.5

Linux distro & Qt version

Windows 11