“Both adding and removing rows in the middle of the pack” doesn’t necessarily mean to follow the instructions I mentioned above.
You have to delete the one RIGHT after the one you just added. (i.e. the one you clicked the + button on, to add the new row)
Yes, I mean the little number at the top-left of each row.
Here’s the screen capture.
http://pasteboard.co/1ZZEPe2U.png
ACF pro 5.2.7
Chrome v43
No error in console.