I believe it to be random. I have all the maps on my hardrive and once in a while, I'll get a qport error. Now I think it comes when loading between maps and noticed that if I do something to disrupt the game during this time, I may end up erroring out and then the qport error pops up. And by disruption, it could be as simple as hitting a keyboard key, as silly as that sounds, that causes an 'unhandled exception' error which then leaves me hanging for a qport error. I am going to test this out of course and on which maps but this is just my own personal observation on my machine.
In the mean, I will be looking at the server files to try different things but as Labob said, there are timing settings that do affect the player in game which I did one time. So the best thing right now is to get a hold of an admin on TS, try disconnecting and connect momentarily to another sever, or as beers suggested, drop out at end of map before the next map reloads (although you will miss the end of match banter and bashing).