Gimbal plus manual servo

Hi,

I have a two-axis servo gimbal working with the integrated gimbal controller connected to AUX1 and AUX2. I am now trying to get a separate servo (AUX5) working either with manual RC control or ideally via MAVlink messages.

extras.txt:

vmount start

mount.aux.mix:

# roll
M: 1
O:      20000  20000      0 -20000  20000
S: 2 0  20000  20000      0 -20000  20000

# pitch
M: 1
O:      25000  25000      0 -20000  20000
S: 2 1  25000  25000      0 -20000  20000

# yaw
M: 1
O:      25000  25000      0 -20000  20000
S: 2 2  25000  25000      0 -20000  20000

Parameters:

Inputs on channel 8 have no effect on the servo at all.
Within the nsh shell the pwm test command moves the servo as expected.

pwm test -c 5 -d /dev/pwm_output1 -p 1100

Does anyone have an idea of what is going wrong here? It’s a Pixhawk with 1.6.1