KF Problem with listen server

[bywatcher]

I have a weird issue with listen server. I host a listen server for me & my friends, they join normally, we play a map. After a map we vote for a new map, map changes and then no one can enter my server. Neither my fiends nor random ppl. Friends say they get stuck at "connecting", while i cant see them even try to connect at game console or server log. Only thing that "fixes" the issue is exiting the game, validating game cache through steam, and downloading 1 mysterious 6.5 KB file. After that i can host a server which my friends can join, till map change.
????
What's going on?

I have mutators(mapvote v2, retrolar, damagepopup, patHPleft) and many custom maps, all compressed and on redirect server. All ports forwarded properly on outer router and pc's firewall.
Any ideas? It's tiresome to do it all again and again every time map changes.

 

[ArcheKruz]

Have your friends clear out the System folder then validate their cache. Also make sure that you have the ports open that are required for hosting.

 

[Tefaan]

I think that's the same issue I have with my second dedicated server. It's down since I couldn't figure out why the hell nobody could connect after a map change. If you figure something out, please tell me. Maybe that could solve my problem too.

 

[bywatcher]

Me and my friends verify game cache regularly. Ports are forwarded properly on both firewall and router. Any other sugestions?