Unresponsive server when debugging

I'm running a 3.0.11 server with Firebird as the backend database. It works very well. I have an issue though when debugging (output to STDOUT): if an authentication query hangs or becomes very slow to respond, during that period of time, the server becomes unresponsive and it can be seen on the log of the nases "Radius server is not responding". Until this happens, it works just fine. If I launch the server without debug, it authorizes all users super fast (except the ones that are very slow), but it don't "hang" the server. It's like in debug mode threads are not used. Is that right? Thanks.