After upgrade to 0.19.1 (windows) I often get connection lost error flashing in red when start the ui. When closing the browser and test again it works.
Same for me. Could fix the error by downgrading the node red dashboard from version 2.9.6 to version 2.9.5. Looks like Issue #411 which was fixed by upgrading the socket.io lib does not always work.
If you want to downgrade the dashboard:
cd ~\.node-red npm i email@example.com
Then restart node red service.
You need to make sure you flush the cache in the browser when you upgrade so that the socket library matches the one at the server end.
Thank you! It works now also in 2.9.6 for me. I had to clear the cache and stop and restart firefox. Now everything is as expected!