My ubuntu server warned me that the TB of storage was getting full which was a shock. Turned out I had 950 Gb of .pm2 error logs and the problem log file was node-red-error.log. It was full of the same message:
Cannot find module node-red
/usr/local/bin/node-red*
But my node red is installed in /usr/bin and is working fine. I tried "which node-red" and it correctly points to /usr/bin
Presumably this is a problem with the way you are using pm2. Are you using that for a reason? The recommended node-red install script for node-red on Ubuntu/Debian/Pi uses systemd not pm2. If you do need to use pm2 then how did you install node-red?