[Users] Double Invites

Hello, I have put my openser box between two sipp generator/server scripts again and I noticed something that might be a problem. Every 200-300 messages i get relayed double invites from the openser. The two invites comming out of openser are only microseconds apart and are for the same message - they have only one invite corresponding from sipp generator. I then noticed that this is happening with other messages too. I am using t_relay and as far as I can see there is no way that two consecutive t_relays are called, since i exit after each relay in my script. Any suggestions? Could this be a config problem. Maybe a bug in the retransmit timers t_relay is using? How can i check if this is the case?

Thanks, Dimitar