InvokeHTTP does't fetch some times - NiFi

[#1]

Hello, 

I've been noticing the past few weeks, that sometimes the proccesor doesn't fetch. 

I have a cluster of 3 nodes. I need to execute one http petition every 15 minutes, so I have a GenerateFlowFile that executes correctly every 15 minutes with a CRON, but the InvokeHTTP, does not fetch

Example of not fetch executions

In the picture you can see that at 17:30, 17:15 and 17:00 it does not execute the fetch, but instead he updates attributes. 

I've not seen any pattern, it's completly random, some days happend, some days not. Sometimes it's just once a day, or anothers happend for more executions a day. 

It does not failure, it just don't execute the fetch. The inputFlowFile is balanced with round robin and it reaches correctly the InvokeHTTP  processor. 

Thanks in advance for the help! 

Greetings