My hardware wasn't actually shutting down by holding the button. I pulled the plug and restarted and then it booted to a screen with a yellow "SHELL>" prompt.
So I downloaded the 2.7.2 installer and put it on a stick and reinstalled from scratch.
Then logged in and uploaded my latest backup.
After a restart it got stuck on this screen twice.
I then pulled the plug again expecting to have to start from scratch, but when it powered on the 3rd time I had my config back.
So I'm up and running again with the latest version installed.
Let that be a lesson to everyone. DO BACKUPS. It saved me hours of time, plus I'm sure I've forgotten all the tricks I learned while setting up the first time.
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