Remove inactive volumes to use the disk. Disk 1,2,3,4,5,6,7,8,9,10,11,12 on a RN4200V2

After creating a topic 2 days ago (https://community.netgear.com/t5/Using-your-ReadyNAS/OS6-stuck-at-booting-mounting-btrfs/td-p/1460789) I noticed this topic which seems to be describing the same issue as I have encountered.

Although I did not describe it in my post (see link above), I had the same situation. I experienced sluggish behaviour, and could not write to the NAS anymore (I could have misattributed the 'not able to write' as sluggish behaviour).

I tried rebooting the system, which, didnt respond to the shutdown (LCD kept showing the  'shutting down' message). After a while I also decided to do a hard reboot of the system.  Afterwards it came up with high load (see my topic), and eventually continued booting but couldnt see the volumes in the admin interface. I have not rebooted my system yet. I am on the latest version of 6.8.x, and had not yet upgraded to 6.9.x.

My dmesg log can be seen at http://www.maxxmark.com/dropbox/nas.dmesg.out.txt and http://www.maxxmark.com/dropbox/nas.dmesg.out.2.txt. And attached a screenshot of the webinterface.

It does feel like a filesystem problem, as it did mount the OS partition. Which, as I understood, is also spread over the disks used for the data. So it feels like the RAID-5 is intact, but the filesystem got corrupted or something.. 

My NAS is out of warrenty for years right now. Is there any way to receive any kind of support on this (even if there has to be paid for it). Although I have an online/offsite backup of my NAS, it takes a lot of time to restore 12TB of data, and trying to recover the partition would significantly reduce retore-time :)