System crasches sometimes when scrubbing

[Agent92]

I've been running my FreeNAS system now for around 6 months and I scrub my pool every 2 weeks. In that time the system have locked up and become unresponsive 2 times around the time the scrub started. The last thing I see in /var/log/messages is:

Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=2219437437939432197
Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=5799102681806304203
Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=357008923246454038
Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=9355982154299264376
Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=12894256296218495257
Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=8357709121706870334
Jun 15 05:00:00 nas01 ZFS: vdev state changed, pool_guid=729225750141273 vdev_guid=6962060013160195102

The next entry is from the next day when I reboot the nas. When I look at the monitor connected to the NAS before reboot I don't see any new information printed and the screen looks kind of weird, it's like a purple and green pattern all over the screen with the console output behind it.

Does anyone know what could cause this or what I could do to maybe catch more information the next time it happens?

I'm running FreeNAS 11.3-U3.2.

My hardware:
1 pool of 6 WD80EFAX drives.
2x SUV500/120G as boot pool.
Intel 6700K
RAM: CMK32GX4M4A2133C13
Motherboard: ASUS Maximus VIII Hero
HBA card: HP H220 LSI 9207-8i
Network card: Intel i350-t2

 

[Alecmascot]

Those screen messages are normal.
You have "gaming" quality kit and it is probably not the best for 24/7 server use.
With a pattern on the screen it probably means a ram failure, perhaps caused by a power supply brown-out.
What PS are you using ?

 

[Agent92]

It's a Seasonic Platinum 660W, probably between 5-10 years old. The NAS is running on a UPS.

 

[Agent92]

I ran memtest now, no errors.

 

[Agent92]

I've ran memtest 4 times now, no errors.