[moadi]

pawn Код:

new bool:landstal[MAX_PLAYERS];

if(GetVehicleModel(vehicleid) == 400)
    {
        if(landstal[playerid] == false || !landstal[playerid])
        {
            landstal[playerid] = true;
            SetPlayerScore(playerid, GetPlayerScore(playerid) + 1);
            return 0;
        }
        else return 1;
    }

If the variable landstal for a certain player gets set to false in other code, it should be the reason the player gets a +1 whenever he enters