Connection Issues:

Some instances of “the host has ended the session”.
Disconnections in the lobby.
Once the lobby reaches 5 or 6 people, random players drop.
After kicking the 6th player from a team, the leader couldn't invite another player
Group leader hangs in the "joining session" screen if the host quits while he is joining.
Improvement of the server selection so that the server is more reactive.
If a player leaves a session immediately when he arrives and they have some packet loss (he is in a resolving state), the resolving time out is not reset and in the next session he will kick all the players as soon as he arrives !!!!
Only 1 disconnect function to each peer when resolving is timed out.

Lag-related issues:

In-game freezing: treats a limited number of Unreal packets per frame to avoid freezes in some specific conditions.
Increased network thread priority over Sound thread that can reduce lag issues.
Fix the case when a player got flashbanged while lagging as a mercenary; the player can remain permanently flashbanged until the player reboot the game.
Fix FPS loss due to a sound problem.

Others issues :

A new Game Version to avoid LAN matches between master and update versions
The loading video was always the same, now it's changed at random
Fixed a bug on the score calculation of the Max Percent challenge.
Challenge Best score is wrong if the player has just beaten it.
Improved checks to avoid accessing an invalid leaderboard
Allows to write leaderboards of live challenges