So quite a few times, hostile survivors uses the trick to disconnect from the server, join a new one, run to a new hideout or behind me, connect to original server to gain advantage.

Also players seem to disconnect when facing problems (Hunted by Zombies, spotted by other survivors etc...)

The solution could be: When a player disconnects, the Character is still in the game, for 1 minute (or less). In that time, the player is vulnerable, and can be killed by zombies and other players.

"BUT WHAT ABOUT US WHO DO NOT PANIC QUIT??" - Well, just like in real life, you have to find a safe place to "sleep" when it's time for that. Adds realism to the game.