pygame.image.load transparent background is sometime showing up white even after I used convert_alpha()

Question

I am trying to import a series of images for an animation in my code using this function:

def import_folder(path):
image_name = 0
surface_list = []

for _,__,img_files in walk(path):
    for image in img_files:
        image_name += 1
        full_path = path + '/' + str(image_name) + '.png'
        image_surface = pygame.image.load(full_path).convert_alpha()
        surface_list.append(image_surface)

return surface_list

But when I run my code some of the images passing by that function exit with a white background even though I used convert_alpha() I even tried changing the image I used and the result is the same Here is the whole code

Main.py:

import pygame,sys
from settings import *
from level import Level
from game_data import level_0

# Pygame setup
pygame.init()
screen = pygame.display.set_mode((screen_width,screen_height))
clock = pygame.time.Clock()
level = Level(level_0,screen)

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    screen.fill('black')
    level.run()

    pygame.display.update()
    clock.tick(30)

level.py:

import pygame
from pygame import surface
from support import import_csv_layout,import_cut_graphic
from settings import tile_size
from tiles import Tile,Static_tile,Crate,Animated_tile

class Level:
    def __init__(self,level_data,surface):
        # General setup
        self.display_surface = surface
        self.world_shift = 0

        # Terrain setup
        terrain_layout = import_csv_layout(level_data['terrain'])
        self.terrain_sprites = self.create_tile_group(terrain_layout,'terrain')

        # Grass setup
        grass_layout = import_csv_layout(level_data['grass'])
        self.grass_sprites = self.create_tile_group(grass_layout,'grass')

        # Crates setup
        crate_layout = import_csv_layout(level_data['crates'])
        self.crate_sprites = self.create_tile_group(crate_layout,'crates')

        # Coins setup
        coin_layout = import_csv_layout(level_data['coins'])
        self.coin_sprites = self.create_tile_group(coin_layout,'coins')

    def create_tile_group(self,layout,type):
        sprite_group = pygame.sprite.Group()

        for row_index,row in enumerate(layout):
            for col_index ,val in enumerate(row):
                if val != '-1':
                    x = col_index * tile_size
                    y = row_index * tile_size
                    if type == 'terrain':
                        terrain_tile_list = import_cut_graphic('/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/graphics/terrain/terrain_tiles.png')
                        tile_surface = terrain_tile_list[int(val)]
                        sprite = Static_tile(tile_size,x,y,tile_surface)
                    if type == 'grass':
                        grass_tile_list = import_cut_graphic('/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/graphics/decoration/grass/grass.png')
                        tile_surface = grass_tile_list[int(val)]
                        sprite = Static_tile(tile_size,x,y,tile_surface)
                    if type == 'crates':
                        sprite = Crate(tile_size,x,y)
                    if type == 'coins':
                        sprite = Animated_tile(tile_size,x,y,'/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/graphics/coins/gold')
                    
                    sprite_group.add(sprite)

        return sprite_group

    def run(self):
        # Terrain
        self.terrain_sprites.update(self.world_shift)
        self.terrain_sprites.draw(self.display_surface)

        # Grass
        self.grass_sprites.update(self.world_shift)
        self.grass_sprites.draw(self.display_surface)

        # Crate
        self.crate_sprites.update(self.world_shift)
        self.crate_sprites.draw(self.display_surface)

        # Coins
        self.coin_sprites.update(self.world_shift)
        self.coin_sprites.draw(self.display_surface)

game_data.py:

level_0 = {
'terrain': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_terrain.csv',
'coins': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_coins.csv',
'fg palms': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_fg_palms.csv',
'bg palms': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_bg_palms.csv',
'crates': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_crates.csv',
'enemies': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_enemies.csv',
'constraints': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_constraints.csv',
'player': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_player.csv',
'grass': '/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/levels/0/level_0_grass.csv'
}

tiles.py

import pygame
from support import import_folder

class Tile(pygame.sprite.Sprite):
    def __init__(self,size,x,y):
        super().__init__()
        self.image = pygame.Surface((size,size))
        self.rect = self.image.get_rect(topleft = (x,y))

    def update(self,shift):
        self.rect.x += shift

class Static_tile(Tile):
    def __init__(self,size,x,y,surface):
        super().__init__(size,x,y)
        self.image = surface

class Crate(Static_tile):
    def __init__(self,size,x,y):
        super().__init__(size,x,y,pygame.image.load('/Users/claudiabergeron/Documents/Python/Tutoriels/Video games/Pygame/Platformer/graphics/terrain/crate.png').convert_alpha())
        offset_y = y + size
        self.rect = self.image.get_rect(bottomleft = (x,offset_y)) 

class Animated_tile(Tile):
    def __init__(self,size,x,y,path):
        super().__init__(size,x,y)
        self.frames = import_folder(path)
        self.frame_index = 0
        self.image = self.frames[self.frame_index]

support.py:

from csv import reader
import pygame
from settings import tile_size
from os import walk

def import_csv_layout(path):
    terrain_map = []
    with open(path) as map:
        level = reader(map,delimiter = ',')
        for row in level:
            terrain_map.append(row)
        return terrain_map

def import_cut_graphic(path):
    surface = pygame.image.load(path).convert_alpha()
    tile_num_x = int(surface.get_size()[0]/tile_size)
    tile_num_y = int(surface.get_size()[1]/tile_size)

    cut_tiles = []
    for row in range(tile_num_y):
        for col in range(tile_num_x):
            x = col * tile_size
            y = row * tile_size
            new_surface = pygame.Surface((tile_size,tile_size))
            new_surface.blit(surface,(0,0),pygame.Rect(x,y,tile_size,tile_size))
            cut_tiles.append(new_surface)

    return cut_tiles

def import_folder(path):
    image_name = 0
    surface_list = []

    for _,__,img_files in walk(path):
        for image in img_files:
            image_name += 1
            full_path = path + '/' + str(image_name) + '.png'
            image_surface = pygame.image.load(full_path).convert_alpha()
            surface_list.append(image_surface)

    return surface_list

settings.py:

vertical_tile_number = 11
tile_size = 64

screen_height = vertical_tile_number * tile_size
screen_width = 1200

Please help me.