fan doesnt work with Intake VOC sensor connected

[Tau512]

I've just built a stealthmax2 and been working on the electronics side.
I've noticed that when i have the intake VOC sensor stack physically connected, then the fan does not work.

i've replaced the rpi picoW, with a second one to hopefully confirm this isn't a device issue - the issue remains.

The only thing I've deviated from wiring instructions is running the rpi on a standard USB cable, and 24v & gnd remains on the microfit 5pin for fan power. I haven't been able to build the USB side (5v, D+ D-) of the microfit connector without the host throwing USB link errors.

controller file is latest current: https://github.com/SanaaHamel/nevermore-controller/releases/download/v1.0/picowota_ota-nevermore-controller_pico_w.uf2, using USB connectivity method.

this issue occurs with both the minimal and a full config. Current config as follows:

# This minimal config is *MINIMAL*.
# There are many extra features that might be worth checking out!
# (e.g. chamber temperature waiting)

[nevermore]
# If you're using USB instead of BT, uncomment and specify the correct serial device.
# WARNING: Make sure it's the `-if02` interface, not `-if00`.
#serial: /dev/serial/by-id/usb-Nevermore_Filter_<board>_<device-id>-if02
#serial: /dev/serial/by-id/usb-Nevermore_Filter_pico_w_E6614103E7717E22-if02
serial: /dev/serial/by-id/usb-Nevermore_Filter_pico_w_E6614103E76A8522-if02

# These `fan_power_*` entries are for a DELTA BFB0712HF (StealthMax BOM)
# If you have a different fan then play with these numbers to the satisfaction.
# See full config documentation for details.
# (e.g. See `fan_power_automatic` if you'd prefer very quiet background filtering.)
fan_power_coefficient: 0.8  # lower max power to keep things much more quiet

# If the fan isn't a DELTA BFB0712HF (StealthMax BOM), you'll probably want to add
#   fan_power_minimum: ???
#   fan_power_kick_start_minimum: ???
# See full-doc for details and some common values.

# Optional
# This 'temperature' sensor only serves to draw the intake VOC index on
# Mainsail/Fluidd's temperature plot.
[temperature_sensor nevermore_intake_VOC]
sensor_type: NevermoreSensor
sensor_kind: intake
plot_voc: true

[temperature_sensor nevermore_exhaust_VOC]
sensor_type: NevermoreSensor
sensor_kind: exhaust
plot_voc: true

[led_effect panel_idle]
autostart:              true
frame_rate:             24
leds:
    nevermore
layers:
    comet  1 0.5 add (0.0, 0.0, 0.0),(1.0, 0.0, 0.0),(1.0, 1.0, 0.0),(1.0, 1.0, 1.0)
    breathing  2 1 top (0,.25,0)

reproduction steps:

• using the above config, turn printer on. note that the fan spins up until rpi has booted and (i assume) initialises the PWM pin. Fan returns to 0RPM. (confirms the fan works)
• note both Intake & exhaust sensor stacks show VOC values.
• manually turn fan on: No change, remains at 0RPM (see below screenshot)

reproduction steps to get fan working:

• turn off printer
• disconnect the SCL/SCA pins to Intake VOC sensor
• turn on printer. Fan pulses and returns to 0RPM while pico boots up.
• Note that Intake VOC sensor has no data, Exhaust VOC shows data
• manually turn fan on. Works as expected. (see below screenshot)