Error sending SmartDocs request from IE 11

[#1]

We are getting a 500 error when we try sending requests from SmartDocs.

This error does not occur on Chrome.

https://community.apigee.com/questions/9620/error-sending-smartdocs-api-request-from-dev-porta.html

The above link seem to refer to the same error but doesn't seem to have been resolved.