9 out of 10 times this message is caused because you run the GetHDFS on multiple nodes. Both nodes see it, perhaps even try to pick it up, but clearly not both of these can delete it. In old versions of NiFi you can fix this by setting the GetHDFS to run only on the primary node. However, that will ofcourse burden the primary node more than it should. So in recent versions (and likely yours) you will find the ListHDFS and FetchHDFS processors (and similar sets for different data sources). The lightweight List processor can then run on the primary node, and loadbalance to all nodes which will then Fetch.
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