1. It not depends on IP of API server behind instagram load balancer
2. It appears on ipv4 and ipv6 both
3. Problem not depends on delay between request code and exchanging this code for token
4. Logout and login helps sometimes
We at smartmetrics.co experience the same issue. We noticed that issue affected not everybody, many customers still can use oauth.
We contacted Instagram and Facebook support but got no answer.
i have made Instagram Analytics for business customers. I will be grateful for any comments how to make it better. Also i'd like to get some advice on how to promote it.