Hey @WONG_TUNG_TUNG,
The error generally indicates intermittent network instability. The driver cancels the ongoing operations to a node when a network timeout occurs (i.e., the heartbeat takes longer than connectTimeoutMS), assuming that a timeout indicates server unreachability. To address this I’d recommend checking out this post and monitoring the network changes.
Also to read more about it please refer to Connection Monitoring - MongoDB Specification. In case of any further questions, feel free to reach out!
Best regards,
Kushagra