selenium.common.exceptions.WebDriverException: Message: TypeError: rect is undefined

今天写python测试脚本遇到这个问题，问题出现的背景是：登录需要操作滑动条，图片吻合后才验证通过。系统是固定十张图片，随机产生；当验证通过后一直报错selenium.common.exceptions.WebDriverException: Message: TypeError: rect is undefined

贴上代码，因为啥帮其他朋友测试，代码比较简易，没时间整理，将就一下；如果有朋友知道解决办法，麻烦留言下，不胜感激！

from selenium import webdriver
from selenium.webdriver import ActionChains
import time
from selenium.common.exceptions import NoSuchElementException
def is_element_present(driver, how, what):
    try:
        driver.find_element(by=how, value=what)
    except NoSuchElementException:
        return False
    return True
driver = webdriver.Firefox()
driver.get('https://www.duoduodaizhang.com/login')
time.sleep(2)
phone = driver.find_element_by_xpath("/html/body/div[1]/div/div/div[1]/div/div[2]/div[2]/div/div[1]/input")
phone.click()
phone.send_keys('1897XXXXXXXX')
password  = driver.find_element_by_xpath("/html/body/div[1]/div/div/div[1]/div/div[2]/div[2]/div/div[2]/input")
password.click()
password.send_keys('XXXXXXX')
button = driver.find_element_by_xpath("/html/body/div[1]/div/div/div[1]/div/div[2]/div[2]/div/div[3]/button")
button.click()
time.sleep(2)
huadong = driver.find_element_by_xpath("/html/body/div[1]/div/div/div[1]/div[2]/div[3]/div/div/div[2]/div/div[2]/div")
action_chains = ActionChains(driver)
for i in range(0,10):
    action_chains.drag_and_drop_by_offset(huadong,200,0).perform()
    if is_element_present(driver,'xpath',"/html/body/div[1]/div/div/div[1]/div/div[1]/ul/li[5]/a[2]")==False:
        continue
    if is_element_present(driver, 'xpath', "/html/body/div[1]/div/div/div[1]/div/div[1]/ul/li[5]/a[2]") == True:
        print('success')
        break

 不稳定的解决办法：

for i in range(0,10):
    action_chains.drag_and_drop_by_offset(huadong,200,0).perform()
    time.sleep(10)
强制休眠十秒，有一定机会成功！