Etherpad: Error raised: Error: listen EADDRINUSE
This error is caused by the port you are trying to listen on is already in use (possibly by Etherpad or another piece of software)
In this case port 9001 was already in use.
To fix this make sure all other instances of etherpad lite are stopped then restart Etherpad Lite.
If the problem still persists try to change the port in settings.json and then restart Etherpad Lite.