Apache NiFI => ListFTP generate duplicate flowfiles when primary node change

[#1]

Hi,

I am running a NiFi cluster with 2 nodes. When I disconnected a node for changing primary, the ListFTP processor relists the listed files. 

  

 I read the ListFTP document at: https://nifi.apache.org/docs/nifi-docs/components/nifi-docs/components/org.apache.nifi/nifi-standard... and see that the: If a new Primary Node is selected, the new node will not duplicate the data that was listed by the previous Primary Node.

But why I met the above situation, can anyone help me?