CSRF and double posting

Code:

$config['csrf_regenerate'] = TRUE;

Disable this setting, it adds nothing to security and will only make your life harder. Especially if you use a lot of AJAX or concurrent AJAX requests.

This is BAD advice, don't listen to it.

The fact that you think token regeneration is related to the described problem, shows that you don't understand how CSRF protection works. Thus, you shouldn't randomly tell people to turn security features Off.