Thanks @Anastasia !
This is very strange because he got the images the same way as usual : an extraction from a video, using VLC !
I tried to upload his original images and they are tagged lynx rufus. For this time, I modified the annotations manually (another example where this would have been awesome : Multi-images "start a new match" (OR do not display separately images that have been the subject of a "start a new match") 
), and I will tell you if this situation happens again in the future 