Thank you for the reply @phillxnet and your work in the write up 
So, I owe a thank you to @suman for the original write up, and a thank you to @HBDK for your updates to the article. Hopefully @HBDK has been able to resolve the Unknown internal error loading Web UI pages issue rendering the appliance unusable from the UI. I noticed that @HBDK had written in the forums about the Linux RAID guide. I gather that @HBDK may have been using the Linux software raid (MDRAID) to manage a RAID10 while I had BTRFS managing a RAID1 at the time the UI was failing on my appliance. I’m still interested in comparing the recovery of an MDRAID to a BTRFS RAID.
And I’ll be glad to send some pictures of the disk and pool page as I have them. They haven’t changed since the setup except for me setting one drive in power standby.
I have some reading to do before I make further changes. So I may just link back to this when I get to rebuilding this MDRAID RAID 1 setup.
Cheers!