I used Intent logic to activate a node. Using exactly the same sentence, sometimes the node was activated, but sometimes it doesn't. I have used both "start as new user" and "simulate timeout event" to create a fresh conversation, however the issue still persisted. Anyone can help advise or throw some light?

seems very unusual. did you try adding utterances to the intent to make it more robust?

@brief-artist-515 when this happens, would it be possible to share a screenshot of the Debugger > JSON > nlu > top facts with items 1 and 2 expanded? like this: