Siren/alarm noises from my server

[BlackHeart]

I've been having an issue with my 9.3 installation. Once in a while, approximately once a week my server will start to sound an audible alarm, like a car alarm or a siren.
It's still running, and I can access the freenas web interface just fine, and there's nothing in the alerts in the top right corner.
I normally solve it by shutting down and restarting the server.

Yesterday the alarm went off again, and I fished out the messages log from /var/log/ - see below.
Does anyone have any idea what's wrong?

Code:

Dec  5 07:23:00 freenas kernel: epair0a: link state changed to DOWN
Dec  5 07:23:00 freenas kernel: epair0a: link state changed to DOWN
Dec  5 07:23:00 freenas kernel: epair0b: link state changed to DOWN
Dec  5 07:23:00 freenas kernel: epair0b: link state changed to DOWN
Dec  5 07:23:03 freenas kernel: ifa_del_loopback_route: deletion failed
Dec  5 07:23:03 freenas Freed UMA keg (udp_inpcb) was not empty (80 items).  Lost 8 pages of memory.
Dec  5 07:23:03 freenas Freed UMA keg (udpcb) was not empty (1008 items).  Lost 6 pages of memory.
Dec  5 07:23:03 freenas Freed UMA keg (tcp_inpcb) was not empty (150 items).  Lost 15 pages of memory.
Dec  5 07:23:03 freenas Freed UMA keg (tcpcb) was not empty (64 items).  Lost 16 pages of memory.
Dec  5 07:23:03 freenas Freed UMA keg (ripcb) was not empty (30 items).  Lost 3 pages of memory.
Dec  5 07:23:03 freenas hhook_vnet_uninit: hhook_head type=1, id=1 cleanup required
Dec  5 07:23:03 freenas hhook_vnet_uninit: hhook_head type=1, id=0 cleanup required

 

[m0nkey_]

Please provide more detail about the hardware as per the forum rules.