3D array not updating as intended or detecting other indexes with itself

I have recently been trying to create Conway's game of life algorithm within python using pygame and changing arrays. However, I have come across a problem where my 3d array will detect elements within the 3d array that become True, that should in reality be false. The issue seems to be somewhere within the 3 functions / loop listed below. If you test the code below the output should be a blinker that switches between a horizontal and vertical line repeatedly.

Full Code:

from pygame.locals import FULLSCREEN
from pygame.locals import DOUBLEBUF
import pygame
import random
import time

pygame.init()

grid_x = 20
grid_y = 20

BLACK = (0,0,0)
GREEN = (20,255,0)

root = pygame.display.set_mode((0,0), FULLSCREEN | DOUBLEBUF)

screen_width, screen_height = root.get_size()

pixelsize = screen_width/grid_x

life_array = [[[0 for x in range(grid_x)] for y in range(grid_y)] for i in range(2)]

life_array[0][3][3] = True
life_array[0][4][3] = True
life_array[0][5][3] = True

def get_adjacent_cells(y,x):

    adjacent_cells = 0

    if y == 0:                
        pass
    
    elif x == 0:
        pass

    elif y == grid_y-1:
        pass

    elif x == grid_x-1:
        pass

    else:
        
        if life_array[0][y-1][x-1] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print("-,-")

        if life_array[0][y][x-1] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print(",-")

        if life_array[0][y+1][x-1] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print("+,-")

        if life_array[0][y+1][x] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print("+,")

        if life_array[0][y+1][x+1] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print("+,+")

        if life_array[0][y][x+1] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print(",+")

        if life_array[0][y-1][x+1] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print("-,+")

        if life_array[0][y-1][x] and adjacent_cells < 4:

            adjacent_cells = adjacent_cells + 1

            if x == 4 and y==3:
                print("-,")

        return adjacent_cells

    #print(adjacent_cells)
'''
    if x == 3 and y==3:
        print(adjacent_cells, ",{},{}".format(x,y))
        #print(x-1)
        #print(life_array[0][y][x-1], " should be false")
'''

def change_cell(y,x,adjacent_cells):
    if cell_alive:

        if adjacent_cells == 2 or adjacent_cells == 3:

            life_array[1][y][x] = True
            print("STIll alive,{},{}".format(x,y))
        else:

            life_array[1][y][x] = 0
            print("dies,{},{}".format(x,y))

    else:

        if adjacent_cells == 3:

            life_array[1][y][x] = True
            print("realive,{},{}".format(x,y))

        else:

            life_array[1][y][x] = 0
            #print("still dead")
    

def check_colour(cell_alive):

    if cell_alive:

        colour = GREEN

    else:

        colour = BLACK

    return colour

    


def check_cell(y,x):

    adjacent_cells = 0

    if life_array[0][y][x]:

        cell_alive = True

    else:

        cell_alive = False

    return cell_alive


'''
for y in range(grid_y):

    for x in range(grid_x):

        life_array[array][y][x] = bool(random.getrandbits(1))
'''


print(life_array[0])

while True:

    pygame.display.update()

    root.fill(0)

    time.sleep(3)

    for y in range(grid_y):

        for x in range(grid_x):


            colour = check_colour(life_array[0][y][x])

            #print(colour)


            y0 = (y*pixelsize)
            x0 = (x*pixelsize)
            y1 = ((y*pixelsize) + pixelsize)
            x1 = ((x*pixelsize) + pixelsize)

            pygame.draw.rect(root,colour,(x0,y0,x1,y1))

            cell_alive = check_cell(y,x)

            adjacent_cells = get_adjacent_cells(y,x)

            change_cell(y,x,adjacent_cells)

    life_array[0] = life_array[1]
    print(life_array[0])



pygame.quit()
        

Any Help would be much appreciated!