What is your operating system?
Windows 10 What is your Shotcut version (see Help > About Shotcut)?
24.11.17
Can you repeat the problem? If so, what are the steps?
While using the “all” button for audio channels, only channel 1 will play with the others not contributing to the sound or waveform. Using 3 channel single track audio with surround 5.1 selected under settings.
The way I successfully tested this is with a DVD VOB file that has stereo English and stereo French audio tracks. When I use Settings > Audio Channels > 4 or 6 and set the Properties > Audio > Track to All, I see 4 channels at differing levels in the peak meter, and I hear both languages in dialog at the same time. I do not have a sample file with a separate mono audio track per channel. I will try to make one with ffmpeg.
I did that with ffmpeg -i VTS_02_2.VOB -filter_complex "[0:a]channelsplit=channel_layout=quad" -vn -sn -dn -channel_layout mono -y output.mka
and reproduced the bug.