preventing multiple authentication attempts for up to 2 minutes.

I am using nlm_python plugin to trigger an out-of-band authentication and get a result typically completed in about 20 seconds but should not time out for two minutes. When I run radtest and a duplicate request comes in I get (0) Ignoring duplicate packet from client localhost port 32940 - ID: 2 due to unfinished request in component authenticate module python in the log. However, in an actual login attempt from a 3rd party system configured to use this radius instance I often see a second authentication attempt almost immediately started while the first is still in progress. How can I prevent this? I set idle timeouts in clients.conf and sites-available/default to 120. What else is needed? Thanks, Jim