[bestia455]

I also get this issue, this only began after I installed the combination of "l4dtoolz + l4d_sm_respawn + superversus + 8survivors (Bill) + Character Select Menu" .... I have ruled out "Character Select Menu" after uninstalling the issue persist. All ports are forwarded, and server is DMZ on router.

Also, it seems if I connect with someone else on the same router, me and the other player will stay in the game after the map loads. If I am in the lobby with 2 other players from the public and start the game the two players from the public drop, however after they're gone if i have the player from on my router connect, while hes loading the maps he sees that me and the 2 others are playing, until the map finishes loading.

Strange, I think uninstalling that cluster of plugins, and mods while just leaving SM+MM+weapon spawner everything will go back to normal.