404 error when uploading file to GCS with query string on Production (Java)

I am using flash to upload a file to GCS.

I create a upload url using the following successUrl

"/cms/requestManager?ps={"1":{"action":"Upload Audio Recording","sendId":1,"data":{"fileName":"testQuestionAudioRecording","category":"testQuestionRecording"}},"jsInstanceID":"ahdzfmRldi1keW5hY3RpdmVzb2Z0d2FyZXITCxIKSlNJbnN0YW5jZRjKm-kBDKIBBmRzLmNtcw","userActive":true}"

When I send the file upload it comes back with a 404 error.

I check in the appengine instance logs for 404 errors and there are none.

The file I tried to upload does show up in the GCS bucket.

In the documentation for blobstoreService.createUploadUrl() it does not mention that query strings are not allowed. I would also expect that if there were something wrong with the successUrl that an IllegalArgumentException would be thrown.

If I go directly to the successUrl it will respond correctly with JSON data.

This is the link if you want to test

On my local test server it works fine. So I am seeing this issue only on production.

If I take out the query string, it will work. If I add a simpler query string like /cms/requestManager?blah=blah it will not work.

Does anyone have any ideas what is going on?

Is there a way to see what is happening on at /_ah/upload?

Could it be possible that it is 404ing on my end but not logging it? If so, what can I do find that out?

Here is the post and response headers and content

Response Header

HTTP/1.1 404 Not Found

Content-Length: 0

Date: Fri, 06 Mar 2015 00:25:25 GMT

Server: UploadServer ("Built on Feb 18 2015 18:10:26 (1424311826)")

Content-Type: text/html; charset=UTF-8

Alternate-Protocol: 80:quic,p=0.08

Request Headers

POST /_ah/upload/AMmfu6a-yuYk7Gm1YMtqLt-GgyizWYLXRStoAZ49FCNNRHIVXMFrRh0Jo1aCSXf4c8uXrjJnCQwvSq7cFdVeI1v5J59jQeVfwvR6STMbs0hBw-GncTI1JHgE4NItQd2JQGgyHIqTasjR4lK_5g8-M0Nf1YdWr29by5Mskk07tpSLNUE0mEW2IOjlWP_Usa7ObJMFdElVqIsgd5a_Bq198AB9oprS6DMHkiYKsdJGCTmHe93w_PEoi-XiROlHSpEsi8TLwQUPPC86iqQsn6th4OGoRudOcdAVhFxCq1VJjXx2frv_Lm0khSxpmOU2nQu8gsbP-IaAgVWMe-0UUgsLYdODjqJhgkr-IB1h05F50pAXTgzImQHyv7ygvOhHO0zGUBAiH1a072LJa7EiN1TXcBYcDfbbMikR5lBdaqfqHccx23RZrDiyGfR3kwMiXmgqFy5BJY5Ht9ZoYlfST76laeM5v2PSheMqweHIZQATBZ0Zxojzv1mFr3ECasfwEY98ambjjrbgqysPwg56B-EYDCwUBAV5FvzY6hIGKnhjun9-rorrx0CuKww/ALBNUaYAAAAAVPj2QZXMlxhUs1-Au6wnswd3PTvLwL_G/ HTTP/1.1

Host: dev-dynactivesoftware.appspot.com

User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:36.0) Gecko/20100101 Firefox/36.0

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Accept-Language: en-US,en;q=0.7,es;q=0.3

Accept-Encoding: gzip, deflate

Cookie: ahdzfmRldi1keW5hY3RpdmVzb2Z0d2FyZXITCxIKSlNJbnN0YW5jZRjKm-kBDKIBBmRzLmNtcw=1425601513386

Connection: keep-alive

appid = dev-dynactivesoftware

successUrl length = 256

Link to blobstoreService.createUploadUrl documentation