It happens on our server on every map.
If it helps it always seems to happen approximately halfway through the second time you get to build stuff, or shortly after starting the second lot of attacking
I think it's a memory leak or something =/
Just like to say as it's my first post on here that you guys have done a great job and the mod rawks. Really interesting way of playing, although most people that play forget about the whole after-you-get-the-flag-you-have-to-get-back thing

other than that is really good