Yeah, this is also strange to me. Btw I found another thread with this issue. Suddenly I visit
this thread today and noticed the header image loaded and disappeared. I tried with Latop and Mobile phone. Both are same. Can you please confirm me someone if you are also facing the issue?
Note: Topic creator also used talkimg to host the images.
Again, this is very strange and I can't figure out why! I took this image, and re-uploaded it as a guest, and it works correctly:

It may be something related to the forum proxy, I don't know. I'll try talking to theymos to see if he has any suggestions.
What I ask at the moment is that when this type of situation is detected, I upload the image again.