Tonat

Compared to the system of m11k, my Helios64 has two 10T Ironwolf disks in slots 1 & 2, other slots are empty.
The mount options are the same except I didn't use nodiratime (I think it is redundant because noatime is used).
Apart from the btrfs scrub I have not had any problems at all.
 
As an experiment I tried the following to see if it would crash again
Do a scrub Simultaneously create two compressed tar files of the data on the disks (trying to produce significant processor and disk activity) After about 6hours I stopped the tars and did another scrub. Simultaneously un-tar the files in step 2 (which finished with expected error as the files were incomplete) Do another scrub. All the above worked correctly.
 
This makes me think the crash originally reported was a one off event (but it would be good to know if there is an underlying cause).
I will let you know if I have any more problems.