I get data sent twice by some agents

This is an odd behavior usually caused by duplication of elements. Check the following settings:

• Existence of two agents with the same agent name. To perform this verification, it can be useful to create a new module in the agent that indicates the IP address of the device (command ip config or ip address depending on the O.S.). This way we can detect the IP addresses of the agents that report with that name.
• Duplicity of modules with the same name. Check that within the agent configuration itself there are not duplicated the module executions with the same name or module and plugin executions that could obtain the same data.
• The module reports more than one data. Verify the module execution locally in the agent and observe that the result of it has only one data.