Plex Media Server Sometimes Requires a Restart?

For the past few months I've noticed that Plex Media Server will become unavailable at random (at both plex.tv and localhost addresses). I'm running PMS on a Mac Mini. The PMS log looks like this:

Dec 24, 2015 10:03:27 [0x700002d19000] DEBUG - Sync: uploadStatus
Dec 24, 2015 10:03:36 [0x700002d19000] DEBUG - PublicAddressManager: Obtaining public address and mapping port.
Dec 24, 2015 10:03:36 [0x700002e1f000] DEBUG - PublicAddressManager: Obtaining public IP.
Dec 24, 2015 10:03:36 [0x700002ea2000] DEBUG - NAT: UPnP, attempting mapping.
Dec 24, 2015 10:03:36 [0x700002e1f000] DEBUG - HTTP requesting GET http://plex.tv/pms/:/ip
Dec 24, 2015 10:03:36 [0x700002e1f000] DEBUG - PublicAddressManager: Got public IP from http://plex.tv: xx.xxx.xxx.xx
Dec 24, 2015 10:03:36 [0x700002e1f000] DEBUG - MyPlex: Last published value didn't change, we're done.
Dec 24, 2015 10:03:39 [0x700002ea2000] DEBUG - NAT: UPnP, found device: <http://192.168.1.1:33988/rootDesc.xml>.
Dec 24, 2015 10:03:39 [0x700002ea2000] DEBUG - NAT: UPnP, usable device: <http://192.168.1.1:33988/rootDesc.xml>.
Dec 24, 2015 10:03:39 [0x700002ea2000] DEBUG - NAT: UPnP, mapped port 20702.
Dec 24, 2015 10:03:39 [0x700002ea2000] DEBUG - PublicAddressManager: Mapping succeeded for 192.168.1.10:20702.
Dec 24, 2015 10:03:39 [0x70000073b000] ERROR - handle_stream_read error 64 Host is down
Dec 24, 2015 10:03:39 [0x70000073b000] DEBUG - Removing notification stream because of error.
Dec 24, 2015 10:03:39 [0x700002ea2000] DEBUG - MyPlex: Last published value didn't change, we're done.
Dec 24, 2015 10:04:31 [0x7000007be000] ERROR - handle_stream_read error 65 No route to host
Dec 24, 2015 10:12:37 [0x7000007be000] VERBOSE - We didn't receive any data from  in time, dropping connection.
Dec 24, 2015 10:15:07 [0x70000073b000] ERROR - CERT: Error in TLS handshake: short read
Dec 24, 2015 10:15:27 [0x70000073b000] VERBOSE - We didn't receive any data from  in time, dropping connection.

(I've stripped my IP address from the log)

You can see that everything is working fine but then there's this error:

handle_stream_read error 64 Host is down

Followed a minute later by this error:

handle_stream_read error 65 No route to host

I can't seem to find any additional information on this. Restarting PMS fixes it every time. Any advice on how to troubleshoot this further??