That's a problem...

Restarted the witness, re-spooned the SWAP and re-registered.

sudo shutdown -r now
sudo swapon /swapfile
sudo systemctl status mongod (with stop|start for good messure ; )
pm2 start app.js --no-treekill --kill-timeout 10000 --no-autorestart --name cervisia
node witness_action.js register

Still getting errors...

2021-03-28 16:27:50 error: [P2P] Error posting to tribaldexwitness / round 122814 / 404 / current round is lower

There appears to be more to typing to do...
will update shortly...