Hi everyone,
Been fighting this for a few weeks but could not figure out why.

My setup:
iNav Firmware version 4.1
FC: Matek F722SE (s4 on the board was burnt, so using s5 on for motor #4)
ESC: Spedix L40 slim
ESC Protocol: Multishot
Motor #2 and #3 are reversed in BLHeli.
When I arm, the airmode will spin the motor; as soon as I move the throttle to about 10%, motor #1 and #4 start to increase speed out of control. The only way to stop them was to cut arm, bring the copter to pre-arm.

Here is the output of my diff all:

# version
# INAV/MATEKF722SE 4.1.0 Feb 28 2022 / 13:50:01 (GITDIR-N)
# GCC-10.2.1 20201103 (release)

# start the command batch
batch start

# reset configuration to default settings
defaults noreboot

# resources

# mixer

mmix reset

mmix 0  1.000 -1.000  1.000 -1.000
mmix 1  1.000 -1.000 -1.000  1.000
mmix 2  1.000  1.000  1.000  1.000
mmix 3  1.000  1.000 -1.000 -1.000

# servo mix
smix reset

smix 0 0 11 100 50 -1

# servo
servo 0 900 2400 1500 -100

# safehome

# logic

# gvar

# pid

# feature
feature GPS
feature LED_STRIP
feature DASHBOARD
feature PWM_OUTPUT_ENABLE

# beeper
beeper -RUNTIME_CALIBRATION
beeper -HW_FAILURE
beeper -RX_LOST
beeper -RX_LOST_LANDING
beeper -DISARMING
beeper -ARMING
beeper -ARMING_GPS_FIX
beeper -BAT_CRIT_LOW
beeper -BAT_LOW
beeper -GPS_STATUS
beeper -RX_SET
beeper -ACTION_SUCCESS
beeper -ACTION_FAIL
beeper -READY_BEEP
beeper -MULTI_BEEPS
beeper -DISARM_REPEAT
beeper -ARMED
beeper -SYSTEM_INIT
beeper -ON_USB
beeper -LAUNCH_MODE
beeper -LAUNCH_MODE_LOW_THROTTLE
beeper -LAUNCH_MODE_IDLE_START
beeper -CAM_CONNECTION_OPEN
beeper -CAM_CONNECTION_CLOSED

# blackbox
blackbox -NAV_ACC
blackbox NAV_POS
blackbox NAV_PID
blackbox MAG
blackbox ACC
blackbox ATTI
blackbox RC_DATA
blackbox RC_COMMAND
blackbox MOTORS

# map

# serial
serial 0 2 115200 115200 0 115200
serial 2 2048 115200 115200 0 115200
serial 5 262144 115200 115200 0 115200

# led
led 0 7,4::C:2
led 1 7,5::C:2
led 2 7,6::C:2
led 3 7,7::L:4
led 4 7,8::G:0
led 5 7,9::C:9
led 6 7,10::C:9
led 7 7,11::C:9

# color

# mode_color

# aux
aux 0 0 2 900 1300
aux 1 51 2 900 1700
aux 2 1 2 900 1300
aux 3 11 0 900 1300
aux 4 10 1 900 1300
aux 5 5 0 1300 1700
aux 6 13 2 900 1250
aux 7 48 3 900 1700

# adjrange

# rxrange

# temp_sensor

# wp
#wp 0 invalid

# osd_layout
osd_layout 0 2 0 0 V
osd_layout 0 9 1 2 H
osd_layout 0 13 23 1 V
osd_layout 0 14 1 11 V
osd_layout 0 22 14 11 V
osd_layout 0 23 1 1 V
osd_layout 0 24 12 2 V
osd_layout 0 30 2 9 V

# master
set looptime = 500
set gyro_main_lpf_hz = 110
set gyro_main_lpf_type = PT1
set dynamic_gyro_notch_q = 250
set dynamic_gyro_notch_min_hz = 120
set setpoint_kalman_q = 200
set acc_hardware = MPU6000
set acc_lpf_hz = 102
set acczero_x = 50
set acczero_z = -86
set accgain_x = 4078
set accgain_y = 4057
set accgain_z = 4044
set rangefinder_hardware = VL53L0X
set align_mag = CW270FLIP
set mag_hardware = HMC5883
set magzero_x = -131
set magzero_y = -34
set magzero_z = 415
set maggain_x = 2798
set maggain_y = 2907
set maggain_z = 1801
set baro_hardware = BMP280
set serialrx_provider = CRSF
set blackbox_rate_denom = 2
set motor_pwm_rate = 2000
set motor_pwm_protocol = MULTISHOT
set failsafe_procedure = RTH
set motor_direction_inverted = ON
set model_preview_type = 3
set applied_defaults = 2
set rpm_gyro_filter_enabled = ON
set gps_provider = UBLOX7
set gps_sbas_mode = AUTO
set gps_ublox_use_galileo = ON
set airmode_type = THROTTLE_THRESHOLD
set osd_video_system = NTSC
set i2c_speed = 800KHZ
set name = XL8

# profile
profile 1

set mc_p_pitch = 44
set mc_i_pitch = 75
set mc_d_pitch = 25
set mc_i_roll = 60
set mc_p_yaw = 35
set mc_i_yaw = 80
set dterm_lpf_type = PT3
set heading_hold_rate_limit = 101
set d_boost_max =  1.500
set antigravity_gain =  2.000
set antigravity_accelerator =  5.000
set smith_predictor_delay =  1.500
set tpa_rate = 20
set tpa_breakpoint = 1200
set rc_yaw_expo = 70
set roll_rate = 70
set pitch_rate = 70
set yaw_rate = 60

# profile
profile 2


# profile
profile 3


# battery_profile
battery_profile 1


# battery_profile
battery_profile 2


# battery_profile
battery_profile 3


# restore original profile selection
profile 1
battery_profile 1

# save configuration
save

# 


Further testing shows that if I set the motor_direction_inverted=off, it would be motor #2 and #3 that would continuously increase RPM regardless of throttle input...

I am thinking this might be something basic that I missed, but couldn't identify anything obvious, might be that I am not looking at the right direction

I posted in the iNav github but later realized that maybe I should have put it here in this forum.

Any help is appreciated.

further update...tried different protocols, DSHOT does not work for my #4 motor (I suppose this is because it is on s5, somehow iNav does not support that); the other protocols, e.g., OneShot125 or Standard does not change the behaviour.

as I suspected, going back to the basics will help...

I changed my direction to check basic concept error...this time I googled "betaflight motor spin up uncontrollable" and I got quite some hits...(unfortunately iNAV as keyword wouldn't come up with many hits...yet)...it turns out that props off on test bench, this is a common "symptom" from how PID works naturally...

So I went ahead and tested with low power battery (just in case my case is different), and it was exactly it...with props on, the copter hovered just fine

the only other observation I had was that even when I landed with low throttle, the RPM will still go up to a certain level from there, I suppose this is due to the iNAV is telling the FC to stablize the copter even when on the ground?