Vehicle isn't executing target depth command correctly

Blue Robotics Software ArduSub
1

Hello again.

I am trying to code a specific target depth. I am using pymavlink to send a target depth command as per the code below. It seems to try to go down to the specified depth but the motors aren’t running continuously. Our vehicle has a density lower than water so our vehicle goes down and up without actually reaching the target depth.

I will post a link to a video of the vehicle to maybe help with diagnosing as well as the code.
I also ran a modified version of this code where the depth target command is sent inside the while loop.-Same thing happened.
Also after the execution of the code, when it comes time to disarm the vehicle, it doesn’t respond. The code waits in the master.motors_disarmed_wait() section until I manually interrupt the code.
has anyone else experienced a similar problem?
I am also sending a yaw value of 60%clockwise and it is not performing a yaw rotation at all.

The Code:

from pymavlink import mavutil
import time


master = mavutil.mavlink_connection("udpin:192.168.2.1:14550")
master.wait_heartbeat()

boot_time = time.time()
print("Successful Connection")


def set_target_depth(depth):

    master.mav.set_position_target_global_int_send(
        int(1e3 * (time.time() - boot_time)), # ms since boot
        master.target_system, master.target_component,
        coordinate_frame=mavutil.mavlink.MAV_FRAME_GLOBAL_INT,
        type_mask=0xdfb, 
        lat_int=0, lon_int=0, alt=depth,
        vx=0, vy=0, vz=0, 
        afx=0, afy=0, afz=0, yaw=0, yaw_rate=0
    
    )


def send_pwm(x =0, y=0 , z = 500, yaw=0 , buttons=0):
    """Send manual pwm to the axis of a joystick. 
    Relative to the vehicle
    x for right-left motion
    y for forward-backwards motion
    z for up-down motion, z -> {0-1000}
    r for the yaw axis
        clockwise is -1000
        counterclockwise is 1000
    buttons is an integer with 
    """
    print(f"running for  seconds, with pwm x:{x},y={y}, z={z} \n yaw:{yaw}, buttons:{buttons}")

    master.mav.manual_control_send(master.target_system, x,y,z,yaw,buttons)


##Arm Vehicle
master.arducopter_arm()
master.motors_armed_wait()

#Flight Mode Setup
FLIGHT_MODE = 'ALT_HOLD'
FLIGHT_MODE_ID = master.mode_mapping()[FLIGHT_MODE]

while not master.wait_heartbeat().custom_mode == FLIGHT_MODE_ID:
    master.set_mode(FLIGHT_MODE)


##Run motors for 20 seconds
tstart = time.time()
set_target_depth(-1.5)
while time.time()<tstart+20:
    
    send_pwm(yaw = 600)

master.arducopter_disarm()
master.motors_disarmed_wait()

The Video Link:
IMG_3424.MOV - Google Drive

Our Power Setup:
We are using a 12V 60A adapter and powering the vehicle directly from the wall. a further voltage regulator brings the voltage to 5V for use in the raspberry and pixhawk. We are using a XT90 pixhawk power module to power the 6 T200 thrusters.

Control setup.
we are using a raspberry as a companion, the Pixhawk as the autopilot and ardusub. I am running pymavlink on my ubuntu computer with python 3.8.10

I can provide further information if necessary.

I had asked this question as a reply to one of the posts I had made earlier so I am putting it here so it can be found easier.