It's ME who thank YOU. Your help has been very useful, as always. Thank you very much for your patience !
Could you share what the cause and solution was?
The problem is that, on your computer, the pictures were received in chunks. I have no idea why it's like that. It seems to happen only to you. Well, only to you, not so sure... In fact, from time to time, my server logs have recorded some users who downloaded a lot of pictures very quickly. At the time, I thought they were users trying to collect all the pictures, but now I suspect they might have been users caught in an endless loop.
Chunked files transfer was introduced by the HTTP 1.1 protocol, so the goal of Test3 was to force the use of HTTP 1.0.
But when I tried Test3 on my computer, I saw that HTTP 1.0 wasn't forced. I looked at my code and saw that I had made a mistake. I've fixed that mistake with Test4 and... Tada !!!