This sounds very like a problem a week or two back. Have you configured node red to autostart on boot? If so then if you disable autostart
sudo systemctl disable nodered
and reboot, then start nodered is it ok? If so then node-red is starting too quickly and the serial port doesn't function for some so far unknown reason. Have a look at this post which tells you how nodered can be delayed on boot, which fixed the problem in this case Serial woes.. buffer issue?
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