File uploads: Warning: session_start(): Cannot send session cookie - headers already sent When I check watchdog, I have lots of PHP warnings like this:


  Warning: session_start(): Cannot send session cookie - headers already
  sent by (output started at
  /srv/bindings/9c42927e5316467d82a6fb1be50ed34e/code/includes/file.inc:1972)
  in drupal_session_start() (line 287 of
  /srv/bindings/9c42927e5316467d82a6fb1be50ed34e/code/includes/session.inc).


There are a lot of reports of errors like this, apparently most of which are caused by having spaces at the beginning or ends of PHP files.  But in this case, I think the problem is related to file uploads for the following reason.  The Location of these warnings are paths like this:


  https://example.com/sites/default/files/styles/profile_pic/public/pics/41207/image.jpg?itok=cdQrU8Rv


The Referrer is my "manage pictures" page, which allows users to add a Picture content type which includes an Image field.

So, it looks like session_start() is having trouble during uploads.  Is there a standard fix fox this kind of problem?
I'm also getting the exact same issue on a Pantheon hosted site. This is on a more complex content type (number of fields) with the image field using the multiupload_imagefield_widget module so we can upload multiple images. The error can also appear on removing an image, where the image field is updated via AJAX. Occasionally, a WSOD will occur.

Location or Path always relates to files/styles/.... 

Tried to duplicate this on a basic content type but it was not occurring. The issue appears on the main content type 80% of the time.