Disk scrubbing followed by fsck TRASHES filesystem?

Actually that was the Netgear case number which I believe is closed.
Here's a few more.
1848 8041
1848 8069

Here's the relevant bits of the communication with the L3 tech:

This is **** from Netgear support. I looked at your case yesterday but since I am based in **** and had left the office, I had requested that one of my colleagues from your timezone follow up with you on this. This morning I can see that this did not happen and I am sorry for this. Unfortunately, the data will not be recoverable in this case. There was an error during the disk scrubbing on April ** and the file system check that ran following this then damaged the file system. Safeguards against this will be included in the 4.2.20 firmware scheduled for release soon. In the meantime, you will need to reset this system to factory defaults and create a new volume. I am sorry for any inconvenience caused. Please let me know if you have any further questions or concerns and I will do my best to address them.

and then after another few questions he confirms that there was an error with the OS configuration that caused my data loss...

> I did notice the release happened after we spoke but did not notice in the
> release notes that it resolves any issues related to raid scrubbing and fsck?
> Are we safe to move forward with this new release or should I be looking
> for a different storage vendor in the interim?

4.2.20 has indeed been released. There is a change in this release whereby it will not run a file system check with auto-fix. Instead it will be read only and will flag any detected errors.

So there you have it. Thank you for confirming that the underlying Netgear OS configuration was to blame.