我參考網路上的教學寫了一個無限滾動式ptt網頁板爬蟲，並且會檢查上一次滾動最尾端的並從那開始繼續爬，不過卻遇到了有機率發生重複寫入同一則文章
有時會突然從某一則開始反覆寫入直到程式滾動次數結束，如圖

有時會從某則開始連續寫入同則後再繼續跑，然後又從之後的某則再度發生同樣的事情，如圖

請問各位大大這是什麼原因
以下是我的程式碼:

import urllib.request as req
import requests
import selenium
import schedule
import time
import json
from time import sleep
import json
import openpyxl
import random
from selenium.webdriver.common.by import By
from selenium.webdriver.common.action_chains import ActionChains
from selenium.webdriver.common.keys import Keys
from selenium import webdriver
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.support import expected_conditions as EC
import bs4




pttWeb = openpyxl.load_workbook('pttweb.xlsx')
ws = pttWeb.active
i = 1


scroll_time = int(input("scroll_Times"))
options = Options()
options.chrome_executable_path = "C:\chromedriver_win32\chromedriver.exe"
driver = webdriver.Chrome(options = options)
driver = webdriver.Chrome()
sleep(3)
driver.get('https://www.pttweb.cc/hot/all/today')
sleep(5)

prev_ele = None
for now_time in range(1, scroll_time+1):
    sleep(2)
    eles = driver.find_elements(by=By.CLASS_NAME,value='e7-right.ml-2')
    # 若串列中存在上一次的最後一個元素，則擷取上一次的最後一個元素到當前最後一個元素進行爬取
    try:
        # print(eles)
        # print(prev_ele)
        eles = eles[eles.index(prev_ele):]
    except:
        pass
    for ele in eles:
        try:
            titleInfo = ele.find_element(by=By.CLASS_NAME, value = "e7-article-default")
            title = titleInfo.text
            href = titleInfo.get_attribute('href')
            ws.cell(i,1,i)
            ws.cell(i,2,title)
            ws.cell(i,3,href)
            sleep(3)

            inner =req.Request(href, headers ={
                    "User-Agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36"
                })
            with req.urlopen(inner) as innerRespomse:
                articleData = innerRespomse.read().decode("utf-8")
                
                articleRoot = bs4.BeautifulSoup(articleData, "html.parser")
                main_content = articleRoot.find("div", itemprop="articleBody")
                boardInfo= articleRoot.find("span", class_="e7-board-name-standalone")
                authorInfo = articleRoot.find("span", itemprop="name")
                timeInfo = articleRoot.find("time", itemprop="datePublished")
                countInfo = articleRoot.find_all("span", class_="e7-head-content")
                board = boardInfo.text
                author = authorInfo.text
                Time = timeInfo.text
                count = countInfo[4].text
                allContent = main_content.text
                pre_text = allContent.split('--')[0]

                ws.cell(i,4,board)
                ws.cell(i,5,author)
                ws.cell(i,6,Time)
                ws.cell(i,7,count)
                ws.cell(i,8,pre_text)
                pttWeb.save('pttweb.xlsx')
                sleep(random.uniform(5,20)) 
                i = i+1
        except:
            pass
    prev_ele = eles[-1]

    print(f"now scroll {now_time}/{scroll_time}")
    js = "window.scrollTo(0, document.body.scrollHeight);"
    driver.execute_script(js)
    sleep(5)


driver.quit()