How do I fix my parallax scrolling background?

Question

So I wanted to do a scrolling background that is fullscreen, no matter which monitor. I used a 7680x2160 background picture which will be scaled down to whatever monitor the user uses, in my case to a 2560x1440 monitor -> 5120x1440 picture For some reason, I get a black bar after every time the background starts again. the error:

I don't want to fix it just by moving it by an amount of pixels that I tested out but I want to find the actual source of the problem and fix it. Does anyone see the mistake in my code?

Also, I'm not sure whether I should use if abs(scroll) > bg.get_width(): or if abs(scroll) >= bg.get_width(): , what do you think?

---

import math
import pygame as py
py.init()
clock = py.time.Clock()

from screeninfo import get_monitors
for monitor in get_monitors():
    FrameWidth = monitor.width
    Top_Bar_Height = 70
    FrameHeight   = monitor.height - Top_Bar_Height

#PYGAME FRAME WINDOW
py.display.set_caption("Endless Scrolling in pygame")
screen = py.display.set_mode((FrameWidth, FrameHeight))

#IMAGE
bg = py.transform.scale(py.image.load("background.png").convert(),(FrameWidth*2, FrameHeight))

  
#DEFINING MAIN VARIABLES IN SCROLLING
scroll = 0
  
#CHANGE THE BELOW 1 TO UPPER NUMBER IF
#YOU GET BUFFERING OF THE IMAGE
#HERE 1 IS THE CONSTANT FOR REMOVING BUFFERING
tiles = math.ceil(FrameWidth / bg.get_width()) + 1
  
#MAIN LOOP
while 1:
    # THIS WILL MANAGE THE SPEED OF
    # THE SCROLLING IN PYGAME
    clock.tick(60)
  
    # APPENDING THE IMAGE TO THE BACK
    # OF THE SAME IMAGE
    i = 0
    while(i < tiles):
        screen.blit(bg, (bg.get_width()*i+scroll, 0))
        i += 1
    # FRAME FOR SCROLLING
    scroll -= 6
  
    # RESET THE SCROLL FRAME
    if abs(scroll) > bg.get_width():               
        scroll = 0
    # CLOSING THE FRAME OF SCROLLING
    for event in py.event.get():
        if event.type == py.QUIT:
            quit()
  
    py.display.update()
  
py.quit()

I tried changing scroll -=6 to scroll -=5 since my monitor_width is dividable by 5 but not by 6 and changed if abs(scroll) > bg.get_width(): to if abs(scroll) >= bg.get_width():, but that did not fix the problem.