I have the same problem.
What on earth is going on?
Wordpress is bad enough in the way it mangles the arrangements of images in edit, so that every time you need to make even a minute change in the text you have to re arrange all the images, and then you can’t tell by looking if you have left the amount of space wordpress wants you to leave….
And when you click update all the images re-scramble – so its always guess guess guess.
Now this new problem emerges and its making me hate WordPress more and more.
Did you ever get an answer you could understand and follow?
Or is it just blowing in the wind?….