On 06/10/2020 12:05, Kenneth Emerson wrote:

root@MythTV:/home/ken# mdadm --assemble --run /dev/md3
root@MythTV:/home/ken# cat /proc/mdstat

Hope I'm not teaching grandma to suck eggs, but you have remembered to 
scatter "mdadm --stop" liberally everywhere between attempts?

Cheers,
Wol