New Add Media doesn't work?

Clearly I am an idiot. They keep making these “improvements” that are supposed to make things easier, but it’s not working for me.
I guess I am stupid. It looks like all you have to do is select all the images you want in the post and then click the button that says Insert Into Post.
But when I do that, nothing happens. Clearly I am missing something.
(I am referring to pictures that I have already uploaded and have been crunched and processed and whatever else it does to them.)

If I pick one picture, it inserts it just fine.
Two or three … yup.
Ten! All inserted.
Eleven – nothing.
So I am now guessing there is a limit of 10 images per post?
If that is the case, is there also somewhere I can change that?

Oh, and it doesn’t save any of the settings I make to the text areas! Ugh.

Thanks!