ReadyNAS 314 stuck on "Booting..." after failed Emby app update

I've been using my ReadyNAS 314 without a problem for several years (I previously owned an NV+ which I've since handed down to my mother and also maintain). Today, I got a notification that a new version of Emby was available. I downloaded and installed it but received an email that the update failed - and that's when it all went downhill.

On the subsequent reboot, the ReadyNAS wouldn't complete the boot process. Here's a rundown of what I tried from that point:

• Initial boot after failed Emby update: Boot process stopped at 95%, at mysqlite
• Next reboot: boot process stopped at 91%, at mysqlite
• Did OS Reinstall – boot stopped at 58%, at fvbackup-q.service
• Forced reboot, same as above.
• Did USB Recovery – successful
• Turned device back on, boot stopped at 96% (fvbackup-q.service)
• Forced reboot, boot stopped at 58% (fvbackup-q.service)
• Attempted OS Reinstall again – boot stopped at 98% (fvbackup-q.service)

I also attempted connecting via SSH, however this also failed. When connecting over my network, using DNS address and IPv4 address, I get this error:
"kex_exchange_identification: read: Connection reset"

When attempting to connect via Ethernet port directly to the ReadyNAS at 192.168.168.168, I get the error:
"ssh: connect to host 192.168.168.168 port 22: Unknown error"

I have tried both Ethernet ports with the same result.

I have a lot of personal data on the ReadyNAS, so I’d like to avoid a factory reset at all costs.

I do have a spare drive that I could use to backup my data via USB, but I'd have to get the ReadyNAS to actually boot up for that to even work.

Can someone please help? I'm desperate, and it seems that Netgear has officially abandoned these devices.