Load balance error - too many redirects

Hello guys!

I have an NGINX server(free version) for my users and want to make it balance connections to 2 java application servers. However, when I activate load balancing via upstream directive using leastconn I get an error in my browser saying "too many redirects".

The network topology is as follows:
- The server is on AWS and accessed via internet
- The users are on a private network behind a NAT to one public IP address

I am guessing that connections get stuck in a loop due to being persistent and lest connection not treating that.
Is this correct? Or am I missing something in the configuration?

Just fyi, if I configure the load balance for ip_hash, the error goes away, but since the source IP is the same, it does not have any practical effects on balancing the connections.

Thanks a lot!

Andre.