I'm on RPi 3 with Raspbian OS v10.7
node-red v1.0.4
node v12.16.1
npm v6.13.4
now i've seen that .node-red folder is under /home/pi.
changes I made are on /usr/lib/node_modules/node-red and i execute (with sudo) npm command on this prompt.
I suggest you start by removing the node_modules folder and also remove package-lock.json (not package.json).
Ok, I made it
Then go into your .node-red folder and run
npm install
in my .node-red folder under /home/pi.....
or
under /usr/lib/node_modules/node-red ???
