Webform does not submit, instead redirects to self My soon-to-be production Drupal site's Webforms have stopped saving submissions; instead it comes back to the same page, complete with the inputted values. I do not have a timeline when it stopped working. In a sandbox environment, Webform 7.x-3.17 works fine.

I'm looking for some suggestions to further debug.

I've tried the following, but to no success:


Disabling any modules that refer to Webform (notably Webform Template and Webform Validation, and my own custom module that had been using hook_form_alter).
Upgrading to the latest Webform (yes I remembered to use update.php).
Based on documentation, combining hook_form_alter($form, &amp;$form_state) with array_unshift($form['#submit'],'my_custom_submit') to insert a custom callback, where I called drupal_build_form($form['form_id']['#value'],$form_state) to emulate a submission.
Obviously flushing caches consistently.
Ensuring that the Webform is published.
Writing a bare-bones module to simply monitor $form_state['executed'] (it always returns false).
Checking my server's error_log both on SSH and FTP.
Checking Reports > Recent log messages.
New: Tried disabling &amp; uninstalling Webform, deleting old Webform files, and installing a fresh new version of Webform; no good.


I'm pretty sure the issue is not isolated to Webform, so it wouldn't make sense to post to their issue queue.

What other debugging methods can I pull out to help crush this bug? If I disable every module without uninstalling, is an entire FTP backup necessary or just SQL?

EDIT: Some more things I've tried as per suggestions (unsuccessfully)


Explicitly defining $cookie_domain and $base_url in settings.php
Looking through Trigger and Action modules for any potential misfiring redirects
I have never had any problem with the Webform module, but if it happened to me I would double check sites/default/setting.php to see if there are any settings for an explicit $base_url or $cookie_domain. The latter is much improbable, since you would probably have problems with logging in.