In the server's config, UDKGame.ini
Default RenX settings:
TotalNetBandwidth=32000
MaxDynamicBandwidth=7000
MinDynamicBandwidth=4000
7000 is the bandwidth per player. 32000/7000 = 16. So, basically under the default value, all servers are only supposed to be hosting 16 players (in the event that they're all using the maximum allotted bandwidth.) Would raising the maximum bandwidth to the correct amount resolve the issue? (For 64 players, totalnetbandwidth should be set to 280000)