What is this? Detection capture, but empty? Is this a person? I don’t know. 
The thumbnail appears to be in error by not showing what it thinks is a person. It is trying to train the AI to recognize if it is seeing a person. I would click the X and it will ask what it is really seeing, you can comment that the thumbnail did not show an image. the X means not a person then you get several options as to what it really is. I get this all the time, it thinks my plant is a human. Your thumbnail should have shown the person seen in the image.
Don’t know
It happens sometimes
Not sure
it does happen to me also sometimes but if I exit and then go back it usually has the picture the 2nd time
Looks human to me
Might be lagging some.