well i think it is a problem of clicking 'next image' too quickly.. having to review an image every 5 seconds or whatever they do.
I have had images required for an image of a man with full face mask on (the image was a close up of the face .. in a mask)
the mask was human like spray painted grey... I can understand why a 5 second review would think it was an actual face, however i did explain what the image was of in the comments.