films_response = requests.get('https://api.themoviedb.org/3/discover/movie?api_key='+TMDB_API_KEY + '&page=' + str(page))  
            movies= films_response.json()  
            for movie in movies['results']:  
                         img = movie['poster_path']  

img generated this way:

*https://image.tmdb.org/t/p/w300/ *+ img
this one is ok : https://image.tmdb.org/t/p/w300/sgCg7dH3BVx7neExreC8D40JcYC.jpg
this one not: https://image.tmdb.org/t/p/w300/9APfNujclgWtS6dALAzgXdPDpGw.jpg

I think something is not correct on your side.