Having the same issue here, according to gproxy logs the server initiates the TCP sesssion closing :
[GPROXY] game started, disconnect protection enabled
[TCPSOCKET] closed by remote host [176.9.26.177]
[GPROXY] disconnected from remote server
[GPROXY] attempting to reconnect
[GPROXY] reconnected to remote server
[GPROXY] rejected by remote server: player not found in any running games
[GPROXY] local player disconnected
[BNET] joined channel [PlayDota.eu]