Intermittent HTTP 403: Forbidden when calling /statuses/update


Getting HTTP 403: Forbidden responses intermittently when posting on behalf of users via REST API v1.1
We use user tokens to authenticate.
Some users report duplicate posts as our app re-sends failed tweets and some of previously “failed” tweets succeed later on.

We are still collecting stats, but it seems that only some of our users are affected by this.

Any help is much appreciated!