Welcome to the n8n community mr.quangdt!
We’ve experienced the same problem on our self hosted instance and indeed others have reported a similar issue before: Code node hanging in n8n cloud
In my case the only thing that helps is to restart the instance. My assumption is that some workflow crashes the worker and when it restarts it doesn’t properly register itself again.
I can only hope this behavior gets fixed soon by the n8n team as this is quite disruptive and annoying.