helem (MIXER, 'Master Playback Volume', 0, 1, 0) appears twice or more cannot load mixer controls: Invalid argument

[GitHub issues - opened]

alsa-project/alsa-lib issue #47 was opened from igrekster:

I have a PCIE Asus Sound Card  (Asus Xonar AE) that uses USB interface:
```
Bus 003 Device 002: ID 0b05:180f ASUSTek Computer, Inc.
```
It's been working fine on earlier versions of  kernel/alsa-lib but at some point the volume control stopped working (the playback still works fine):

```
$ alsamixer -c 1
ALSA lib /var/tmp/portage/media-libs/alsa-lib-1.2.2-r1/work/alsa-lib-1.2.2/src/mixer/simple_none.c:1544:(simple_add1) helem (MIXER,'Master Playback Volume',0,1,0) appears twice or more
cannot load mixer controls: Invalid argument
```
This is on kernel 5.4.37/alsa 1.2.2. Unfortunately I cannot downgrade to the point when it was working to pinpoint the issue. I tried kernels 5.3.11 and alsa 1.1.8.
I've tried building the latest alsa-lib, and it is still showing the error.
I'm happy to try patches to alsa or kernel modules to help debug this.

A few more details:

[alsa-info.txt](https://github.com/alsa-project/alsa-lib/files/4569764/alsa-info.txt)
[proc-asound.txt](https://github.com/alsa-project/alsa-lib/files/4569766/proc-asound.txt)

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/47
Repository URL: https://github.com/alsa-project/alsa-lib