While scraping a website I encountered a strange behaviour, running the script multiple times gives variable results. Sometimes the number of elements obtained by find_all is the expected one, others instead I find duplicates, after using set() I obtain the same elements as before.

soup = BeautifulSoup(driver.page_source, 'html.parser')
cards = soup.find_all("div", {"class": "product-card__body"})
print(len(cards))
print(len(set(cards)))

I have tried looking at the differences in the html source but still I couldn’t figure it out. Using selenium I couldn’t notice differences in the two runs.