The only problem which it could be caused by is that, because you (the user) is locked on the loading page like that, then when the grabber keeps trying to gather usernames which do not exist... it must for some reason f*ck up and mess the list up with it. That shouldn't really happen but that's all I can think of.
What will I do to prevent this?
1. I will add a background function to COMPLETELY reset the game instance every half hour. This means that the list will be kept, but it will stop the lag from occurring as much and prevent people from being locked on a loading screen.
2. Simply stop the grabber from searching for usernames if the map is loading or the game is on the login screen. (if it's not already there, I haven't worked on it in a while)
For now, there isn't really a way of fixing it unless you constantly watch the grabber and make sure it doesn't get locked anywhere for some reason. The only other thing which users can do is get the right balance between their connection and the speed at which they want to grab usernames (server choice). If any user is on a bad connection, then they should only use low populated servers to be honest :P