I had Drupal 7 and when I want to delete user, an error occurs:
AJAX HTTP error occurred.
HTTP status code: 200 Debug information below.
Path : /batch?id=1594&op=do
ResponseText : #Screenshot
It was a server error so Drupal send many request at once but the server have a miximum execution time. I suggested for my client to change it and it works fine now.