Some troubles with my custom sound card

Hardware
1

I’ve got a custom wm8731 board that I’ve designed by following the Wolfson reference design. It just adds some extra pins for testing different line in preamp stage. It use a 12MHz crystal as the audioinjector, so that is the setting I’ve selected in the webconf.

Aplay -l (and arecord -l) shows the audioinjectorpi device.

card 2: audioinjectorpi [audioinjector-pi-soundcard], device 0: AudioInjector audio wm8731-hifi-0 [AudioInjector audio wm8731-hifi-0]

But, as is, jackd isn’t loaded at startup (jack_wait). I have to stop zynthian and jack2 service, and then start jack2 service to get it up and running.
Ok, let’s solve this problem later because even with jackd running, zynthian won’t start.
UI log tells me:

Jun 01 13:14:36 zynthian startx[1171]: Cannot read socket fd = 7 err = Success
Jun 01 13:14:36 zynthian startx[1171]: CheckRes error
Jun 01 13:14:36 zynthian startx[1171]: JackSocketClientChannel read fail
Jun 01 13:14:36 zynthian startx[1171]: Cannot open jackpeak client
Jun 01 13:14:36 zynthian startx[1171]: JackShmReadWritePtr1::~JackShmReadWritePtr1 - Init not done for -1, skipping unlock
Jun 01 13:14:36 zynthian startx[1171]: JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
Jun 01 13:14:36 zynthian startx[1171]: libjackpeak failed to start jack client: 33

and

jack_lsp -c outputs:

Cannot read socket fd = 5 err = Success
CheckRes error
JackSocketClientChannel read fail
Cannot open lsp client
JackShmReadWritePtr1::~JackShmReadWritePtr1 - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
Error: cannot connect to JACK, jack_client_open() failed, status = 0x21

Ok, let’s stop jack2 and perform a basic aplay test:

aplay -D hw:2 /usr/share/sounds/alsa/Noise.wav
Playing WAVE ‘/usr/share/sounds/alsa/Noise.wav’ : Signed 16 bit Little Endian, Rate 48000 Hz, Mono
aplay: set_params:1349: Channels count non available

Specifying -c2 or -c1 in aplay parameter doesn’t change anything: same error message.
Any advice for investigating that further ?