The latest update is causing the servers to crash without warning. They are not saving data prior to the crash so you may lose up to 15 minutes of activity or spawn in a spot where you were 15 minutes prior to the crash. This could drop you right into the middle of a zombie spawn. It'll be fixed whenever Nelson gets around to fixing it.
No idea when the server issue will be resolved. I haven't seen anything about a fix. I can't tell if the servers are running, but players are unable to connect, or if the servers are truly down. That means the status of bases is unknown. If the servers are running but no one can connect, they will despawn.
Cory managed to catch some information in the error logs for PvE1 and PvE2 earlier today and sent it off to Nelson. Nelson replied and said it looks like a Unity issue and he might have something by the time of the next update! It was very good to get a quick response to what what shown in the error logs. Cross your fingers for the fix!