I'm sorry to say that you may not find much assistance for your problem, primarily because you are running FreeNAS 8.3.
I will try to give you some advice and I'm sure someone else may chime in. Here are my questions for you to answer, please be as descriptive as possible, treat me like and idiot that has no clue what you are talking about this way we limit assumptions and I can provide the best answers in the shortest amount of time.
1) What kind of pool are you using, ZFS or UFS?
2) Are all of your hard drives attached to FreeNAS, no errors?
3) Run a SMART short test on your drives, ensure they are responsive.
4) Post the output of all drives that you ran the SMART test on, use the "code" blocks to retain the data format.
5) Do you have a backup of your FreeNAS configuration data? If not make one even though it may be too late for it to not be corrupt. We might need this.
6) Post the output of zpool status
and zfs list
in code brackets.
7) What is your boot device? If this is a USB Flash drive then you may need to obtain a different device but lets just see what else you come up with.
I'll stop there as this will help identify the viability of your hardware and basic configuration. I suspect that your problem isn't Plex but more so a failed piece of hardware.