Error uploading file. An unrecoverable error occurred I've been troubleshooting a form in Drupal 7 that has two file upload fields.

If you upload a file with one field, then the other, the second upload will usually give an error. This occurs regardless of the order that the files are uploaded. The error does not occur if the files are both added to the "Choose File" fields and the whole page is submitted at once with the save button. The error also does not occur if JavaScript is disabled in the browser, and the individual upload buttons are used.

The easiest workaround I can imagine would be to disable javascript for the form controls on the specific /node/add page, but I do not know how to do this, and I have been unable to find people with a similar need.

The server is PHP/Apache2, with mod_security disabled and with the PHP post size limit and uploaded file size limit set to high limits as per the screenshot. File uploads work normally, leading me to rule out permissions as a culprit.

The watchdog logs and server error_log have no messages of interest, unfortunately.

If anyone has any advice to disable javascript for a page, or to resolve this error, please let me know. Thanks!
This error is for this line in file.module 
241 --if (empty($_POST['form_build_id']) || $form_build_id != $_POST['form_build_id']) {

You should revise your URL