After following up some problem, I now can't start the Docker service.
Firstly I was adding a new docker, but it failed because of a read error.
I checked system logs, saw a bunch of "BTRFS error (device loop2): parent transid verify failed" errors.
I tried to stop the array but it never finished the process, I tried to safe reboot but it wouldn't so I pulled the power.
After rebooting, eventually searching the forums led me to delete the Docker image
When I turn the Enable Docker again, the page just loads forever.
Refreshing the page shows that Docker still has not started, the bottom Unraid status bar says "Starting Services"
The Tools > System log shows this on the last line
"Sep 1 20:15:16 Starbuck nginx: 2020/09/01 20:15:16 [error] 1993#1993: *2041 upstream timed out (110: Connection timed out) while reading upstream, client: 192.168.1.13, server: , request: "POST /update.php HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "starbuck", referrer: "http://starbuck/Settings/DockerSettings""
Cheers
starbuck-diagnostics-20200901-2016.zip