A few temporary measures have been announced through the official Metal Gear Twitter account, meant to combat the connection issues people are having.
We’re seeing connection issues and are taking temporary measures:
1. Number of FOB missions displayed decreased.
2. Win/Loss, Points, Support and Heroism info on the FOB MISSION list has been disabled.
3. Number of missions listed in online COMBAT DEPLOYMENT menu has been decreased.
We apologize for this and will update further.
Hopefully this will help fix the problems people are having.
Source: Metal Gear Official Twitter