[Users] Delayed signalling?

Hi all, Just wondering if anyone else has had this problem. I have noticed while tracing on my OpenSER server, that every now and then the server receives a packet which it does to respond to immediately, resulting in a string of packets being sent to the server and then the server responding a few seconds later. This does not happen all the time, just say maybe once or twice every hour. The rest of the time the signaling is correct and responses follow request packets in the correct order. What I am trying to figure out is whether this is a load traffic issue (i.e. can the server not handle too much load), and if so is it OpenSER or the network or the server in general? I have run diagnostics on the servers and there is nothing wrong with the hardware. On the other hand Could this be related to any timer issues? I remember there was mention of timers in SER but are there any default timer settings that can be tweaked? Thanks in advance for any response.