Pwm aux disarmed not working


I’m trying to set the pwm disarmed value to 1500 as my 8 aux channels are servomotors.

The airframe file looks like this (after calling sh /etc/init.d/rc.mc_defaults)

set MIXER_AUX pass8
set PWM_AUX_OUT 12345678
param set PWM_AUX_DISARMED 1500
param set PWM_AUX_MIN 1000
param set PWM_AUX_MAX 2000

The first 4 aux seems to work but the channels aux5 to aux8 have strange values.
Here is a screenshot when the vehicle is disarmed.

I also tried to set it from the QGC Mavlink console

pwm disarmed -a -p 1510 -d /dev/pwm_output1

It does change the field disarmed: 1510 us for all channels, but the actual value when the vehicle is disarmed does not change.

Am I missing something? Is it dependent on the aiframe number ? (I expect no)