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

[GitHub issues - edited]

alsa-project/alsa-lib issue #47 was edited 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.

```
$ amixer -c 1 controls
numid=7,iface=CARD,name='Clock Source 18 Validity'
numid=10,iface=CARD,name='Clock Source 19 Validity'
numid=17,iface=CARD,name='Clock Source 22 Validity'
numid=11,iface=CARD,name='IEC958 In - Output Jack'
numid=18,iface=CARD,name='Keep Interface'
numid=14,iface=CARD,name='Line - Input Jack'
numid=12,iface=CARD,name='Mic - Input Jack'
numid=8,iface=CARD,name='Speaker - Output Jack'
numid=20,iface=MIXER,name='Master Playback Volume'
numid=19,iface=MIXER,name='Master Playback Volume',device=1
numid=5,iface=MIXER,name='PCM Playback Switch'
numid=9,iface=MIXER,name='PCM Playback Switch',index=1
numid=16,iface=MIXER,name='PCM Capture Source'
numid=15,iface=MIXER,name='Line Capture Switch'
numid=13,iface=MIXER,name='Mic Capture Switch'
numid=6,iface=MIXER,name='Input Gain Pad Control'
numid=4,iface=PCM,name='Capture Channel Map'
numid=1,iface=PCM,name='Playback Channel Map'
numid=2,iface=PCM,name='Playback Channel Map',device=1
numid=3,iface=PCM,name='Playback Channel Map',device=2
```
`amixer -c scontrols` fails withe the same error as `alsamixer`.

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