Another round of testing as I'm now confused as well.
All three images uploaded to the post and pulled up from the sub-image holding area by dragging and dropping -- order and sizing remained consistent.
Edited the post by removing the images from the body of the editor (not the sub-menu holding area as it said deleting the attachment will delete it from the Forum permanently (as these have been used in my G97 thread was concerned that it meant they would also be deleted from that thread or wherever they may also be residing which I don't want) - so that begs another question, is it possible to delete images from a post but not the Forum as they are given identifiers now rather than the name of the image?. I added all text only to the now blank edited post (but the images still in sub-menu), and then could pull them up and place in between paragraphs correctly without sizing or ordering errors.
Even if I remove all of my text and do not place the images back up into the thread, the images still show though, but this time in the order as shown in the sub-menu, so I guess one does have to delete them completely by clicking the image's 'x' (which I will if you guarantee they won't also be deleted in my other threads?).
Not sure this helps as I'm honestly confused now, but just trying to report this isn't how it was working so maybe you've seen enough on your side to catch something?