OAuth2 server returns faulty access tokens for first few tries

I'm using lucadegasperi's OAuth2 for Laravel 5.1. My server is hosted on ElasticBeanstalk EC2, and my client is my app hosted on AWS S3. Both are served through CloudFront with an attached certificate.

When I request an access_token for password grant type from localhost frontend to my localhost server, I get a valid token every time.

When I push both to production (S3 and EC2 respectively), for the first 5 or 6 tries, the returned access_token is not valid. After the 6th request, all the tokens seem to work. Deploys change nothing about the OAuth process/request.

This only tends to happen when my app is making the request, as requesting via Postman to production always returns a valid access token. Could it be something to do with S3?

I thought this may be due to Cloudfront stripping the headers, but Authorization header is whitelisted:

via Chebli Mohamed