OK - I'm normally on other end of such problems but I'm sitting here stumped as to where to start with this one!
I had a Pi3 connected to Neopixel cube, programmed with Node-RED and decided to take it to a Raspberry Jam to show it off last night.
I (very foolishly and I don't really know why I did it) decided to run the standard bash script to upgrade it from 0.19.x to 0.19.2 and now it simply locks up the whole Pi (becomes completely unresponsive over VNC and has to be rebooted) once the flows start up
I launch NR on my Pi by cd ing to /home/pi/.node-red and then typing node-red
it all is fine until the flows actually start running and then I can't do anything (Pi shows no activity on green light) and few secs later my VNC connection fails)
JFI - I have disconnected the Neopixels and it makes no difference and the same Pi works fine using another card so its not a hardware issue :slight_smile
rename/backup your flow so that it starts with a blank flow - and then either start over - or re-import your original flow (via cut/paste) and try to work out what needs fixing before you hit deploy.
And I simply opened up the old flow in my editor - copied it to clipboard - imported into NR editor - deleted the default blank Flow 1 - de-deployed - all good - rebooted Pi - still all good
Run tail -f /var/log/syslog in a terminal and then start node-red in another terminal, it may show something useful.
Also if you are using MQTT then stop the MQTT server(s) and try again. For me an MQTT loop is the most common sort of clog up you describe.