JorgeB

Unassign the cache pool device, start array, stop array, make sure the pool only has one slot, re-assign the NVMe device, start array, post new diags.

Avoid using controllers with SATA port multipliers, more info below:
 
 
 

failed to start daemon: write /var/lib/docker/volumes/metadata.db: no space left on device  
Try recreating the docker image:
https://docs.unraid.net/unraid-os/manual/docker-management/#re-create-the-docker-image-file
Also see below if you have any custom docker networks:
https://docs.unraid.net/unraid-os/manual/docker-management/#docker-custom-networks

Check filesystem on cache, run it without -n and if it asks for -L use it.

Docker image in the diags was corrupt, you can just recreate:
https://docs.unraid.net/unraid-os/manual/docker-management/#re-create-the-docker-image-file
Also see below if you have any custom docker networks:
https://docs.unraid.net/unraid-os/manual/docker-management/#docker-custom-networks

Mar 23 09:27:12 Tower kernel: ata3: limiting SATA link speed to 1.5 Gbps Mar 23 09:27:12 Tower kernel: ata3: SATA link down (SStatus 0 SControl 310) Mar 23 09:27:17 Tower kernel: ata3: limiting SATA link speed to 1.5 Gbps Mar 23 09:27:18 Tower kernel: ata3: SATA link down (SStatus 0 SControl 310) Mar 23 09:27:19 Tower kernel: ata2: limiting SATA link speed to 1.5 Gbps Mar 23 09:27:20 Tower kernel: ata2: SATA link down (SStatus 0 SControl 310) Mar 23 09:27:21 Tower kernel: ata3: limiting SATA link speed to 1.5 Gbps Mar 23 09:27:22 Tower kernel: ata3: SATA link down (SStatus 0 SControl 310) Mar 23 09:27:24 Tower kernel: ata2: limiting SATA link speed to 1.5 Gbps Mar 23 09:27:24 Tower kernel: ata2: SATA link down (SStatus 0 SControl 310)  
Issues with multiple devices, likely a power/connection problem

You can try with a different PSU for example, you can also boot Windows from a live flash drive and run some tests.

Delete the disklocation plg file from /config/plugins and reboot

Looks like a power/connection issue, and the CRC errors point to the SATA cable, try again when you get a new cable.

Still errors on disks 3 and 4, make sure you also check/replace the power cable, any splitters in use?

Disk should be replaced.

Just copy the data back from the backup, you can use for example rsync, it will only copy the missing data.

Swap both cables with the other disk, if the problem follows the disk it's likely failing.

Check filesystem on disk1, run it without -n, and also run a correcting scrub on the pool.

I would try to create a new Windows VM, if it works correctly point the new VM to the old vdisk and re-test.

Can only tell that it's not a general issue, since many users, including myself, can get 2.5GbE in both directions.
 
 

I'm afraid there's no trace of a filesystem signature on any of the two partitions start sector Unraid can possibly use, are you sure those disks were ever formatted?
 
If yes, either the partition is truncated or the disk was fully wiped, in any case I don't an option to recover, maybe UFS explorer, if the disk was not fully wiped.

Updating the Connect plugin should fix that, though like mentioned you should update them all.

You can do a new config and re-sync parity, and if you still want the SSD in the array re-format it at that time, but make sure you update to v6.12.8 first.

Mar 22 08:31:13 Tower kernel: md: disk1 write error, sector=976762608
Still write errors, SMART looks OK, but it can still be failing, swap both cables with a different disk and re-start the array, if the same the disk is likely failing.

Did you check if they have a blank space in the end? That can cause what you are seeing, you can also try disabling mangled files on Samba, but then, they might no show up over SMB.

Pool cfs is configured for single, unassign all pool devices, start array, stop array, reassign all pool devices, start array, after this you should be able to remove the device.

Did you try recently? There was some site maintenance going on a few hours ago.

Looks more hardware related to me, one thing you can try is to boot the server in safe mode with all docker containers/VMs disabled, let it run as a basic NAS for a few days, if it still crashes it's likely a hardware problem, if it doesn't start turning on the other services one by one. 

See here for a workaround:
https://forums.unraid.net/bug-reports/stable-releases/6128-no-webgui-run-full-r2854/?do=findComment&comment=27334