Solved Players changing their Steam ID (non-Steam)

Hi all. Help me please. Yesterday i reboot my internet modem when the server was launched. (server is locally on my pc). there are was 2 players on the server. after that they are entered the server, but one of them became a new character, because him client, or my server has changed him steam id. He has a nickname same as him original character, but it was new character. after that he left server and restart him client, and enjoy to server in the old original character. So my question - what it was? Now i had 2 different players with this problem and i dont know what to to. Help me please, or give a link to forum with this problem. Thank you all very mush!
P.S. Sorry for my english)))

 

Hi. Thank you that rename my Title. But not the players change their ID, it changes itself, and after that player must play by new character. And yes, i use non-steam server.

 

ok. Thanks (