It probably annoys a few of us who want to do montages or whatever (For us machinima makers, we should be in spec anyways. ) if we record a demo we freeze up with a NetChannel type error sending Fragments, and you get caught in a fragment loop until you re-join. It happens in Garry'smod,- but in GMod it only happens after the server has been on a map for too long. I just think that you guys should be aware, only seems to affect players, and not spectators. Haven't tried it as a commander. Would be nice to be able to record demos for demo smoother or for a video tutorial whatnot.
I usually only have this problem if I have been on the server for a while, as you said happens in GMod. Even then it only happens about half the time. It seems pretty random to me.
I think it might be how much data is going on-- Like a cup getting a drop of water every time a physics calculation goes on, a person moves, a bullet fired, a building built, etc. Eventually that cup gets full. The demos say "NO U" at you, and give you fragments.