NV+ - No fileshares - no frontview

Sorry about the late answer.
My desktop has been out of bussiness, so I had to "awaken" it this weekend before i could proceed with the disk-testing.

I first tried your 2nd suggestion (the log files) since this didn't require any preparations.
I'm not exactly what I would describe as "comfortable" with linux commands, but I know the basics and google is my friend so based on other similar threads I gave it a go.

To trace back what I did

1. Started techsupport, holding the power button for 15 sec when turning on

2. Logging in using root/fr8ntview (i think)

3. Found an instruction, telling me that 

# /bin/start_raid.sh
# mount /dev/hdc1 /sysroot

would be the way to go

4. Did these:

# /sysroot/bin/df -h

# /sysroot/bin/df -i

# /sysroot/usr/bin/du -csh /sysroot/var/*

# /sysroot/usr/bin/du -csh /sysroot/var/log/*

5. Found that sysroot/var/log/upnp-av.log is 1.2 ?B and full of:

[2017/08/11 17:39:22] minidlna.c:1294: error: accept(http): Too many open files

It had been filling up since 2013 until 2017 (11 aug, which might very well be when the NAS failed)

(**Right now I'm kicking myself, cause I'm actually not sure wether the file was 1,2GB or 1,2TB. In my head at the time it was 1.2TB which could explain the disk beeing full, but in my notes I've written 1,2GB which is "nothing". I did though recall that it reported the disk as 99% full before I emptied this file, but I'm not entierly sure. I do however don't think that this affects the current state, as I now know that "right now" the drive isn't full****)

6. Did a

#echo  > upnp-av.log

to empty the file

7. Rebooted the server, did an OS-reinstall, but no luck.

This weekend tested my disks. Two of the samsungs and the WD completed the test in 5,5 hours (each) with no errors. The last samsung (which is the disk in slot 1) failed, giving a log of LBA errors (failed sectors). I think the whole test took about 10 hours (although it's identical to the other samsung disks).

So - I'm just speculating - Is the OS located on the disk in slot 1?
Could the situation I'm seeing with the LEDs be that the NAS is neither capable to load or update the OS due to disk-failure?
If I did a low level format of this disk and reinserted it in slot one, should the NAS reinstall the OS and rebuild the disk from the XRAID?

I the above is the way to go, I could of course buy a new 2TB disk to be safe, but as the NAS is old and I'm considering a new one, this would be wasting money on a disk it's unlikely to ever use for anything else. Even worse, it's a complete waste of money if this doesn't fix my problem (that's why I would try formatting the disk before buying a new one)

Sorry about the long post, just trying to provide as much information as possible, any input is appreciated.