from comment: https://www.drupal.org/node/2034051#comment-8136969

Looks like something is breaking load sequence. In my situation (invalid comments #6 and #7) the reason was REL module, which simply did drupal_add_js('misc/ajax.js'); and this was breaking weight of already prepared ajax.js library.

Can ajax.js be loaded conditionally?

Comments

SocialNicheGuru’s picture

SocialNicheGuru CreditAttribution: SocialNicheGuru commented

should it be changed to drupal_add_library like in this issue:
https://www.drupal.org/node/2034051

replace 

drupal_add_js('mis/ajax.js');

with

  drupal_add_library('system', 'drupal.ajax');
sinasalek’s picture

sinasalek CreditAttribution: sinasalek commented

There is another issue but it's not resolved completely #1532566: AJAX should be loaded as library to prevent conflicts with other modules