At least for me it seemed to have improved with the patch 1.13 (stating Changes have been made to reduce the chance of being disconnected from a game session. ). Only one case of NM14 in November and since then no problems anymore. Also using Windows 10, DRX 11. EDIT: I shouldn't have said it... Today (2.1.) NM14 again when trying to join the weekly event.
Also got NM14 on the weekly event (this week and last week). Unfortunately you cannot join any other session then but have to wait another hour. This is quite annoying as I cannot wait hours a weekend to join a session hosted by a player with good internet connection. Why aren't these sessions hosted by codemasters? Another solution would be to transfer the host to one of the other players trying to join. That would definitely increase the chance to join the weekly event. CC @BarryBL