EX4100 going into nightly System Under Temperature warning, making it unusable

My EX4100 on a regular basis is showing System Under Temperature status, and unmounting all connections to it from my desktops that are serving up Plex.

The temperatures of the disk are 27C, 28C, 28C, (0C), 28C … not sure how this is showing that it is at “freezing”.

The NAS is in my basement beside a MyBookLive Duo, my modem, theatre room receiveer, PS4, etc, and none of these devices have had issues (or feel that cold!!). It does get a little cool in my basement at night, but nothing that is overly cold.

Any ideas as to how to overcome this?? I’ve put it in an area where it can be ventilated… do I need to wrap a blanket around it or somethign???

System temperature is not the same thing as disk temperature.

But it sounds to me like the thermal sensor for the system is failing, if I had to guess…

Thanks - is there a way to run a diagnostic on it?? If that’s the case what would you recommend doing?

I believe I have a very similar problem…
I have two EX4100 stacked
The bottom EX4100 shows 28C and has a fan speed of 1935 rpm
The top EX4100 shows 38C and has 618 rpm fan speed

I have never had a problem like that before
it happened hours after upgrading to OS5

First after upgrading to OS5, I had a failing drive - Drive SMART Failure
Drive status FAULT
RAID status degraded
I submitted the disk to the WD Data Lifeguard Diagnostic tool, and after 30+ hours it had found some bad sectors.
After fixing them, the notice that I need probably to rebuild the drive.
I put the drive back, and booted the EX4100.
First try to rebuilt failed with message
“Volume Rebuild Failed
Volume 1 rebuild has failed. Check the system’s drive status by running Disk Test in Settings / Utilities”

So, I shutdown, removed the drive, and fixed it on my old Windows 7 machine. Just run SMART check with success. I warm inserted the disk back into the EX4100, and after nearly a day the RAID was rebuilt OK.
Today, after boot, the system fan on max speed (1935 rpm), and system showing 28C ( ¿ under temperature ?)
I cannot connect to the web server via browser - refused to connect -
after reboot, everything is normal again -

BUT - after about 30 minutes, the EX4100 running full system check can no longer be accessed (38C/631rpm)

I am starting to DESPAIR…