Japanese

When testing a synchronous BPEL process (which internally invokes a REST web service) from the Oracle Enterprise Manager 12c console or from Postman it sometimes fails but other times it works.
The JSON object I send in the request is:

{
    "customer": {
        "taxIdentificationNumber": "12xx"
    }
}

And the expected response is:

{
    "customer": {
        "birthDate": "1999-10-18T00:00:00-05:00",
        "firstName": "WalterXXXXXX",
        "lastName": "BatesXXXXXXXX",
        "taxIdentificationNumber": "12xx".
    }
}

But sometimes the response is the following error:

{
    "RestFaultElement": {
        "summary": "faultName: {{http://docs.oasis-open.org/wsbpel/2.0/process/executable}selectionFailure} "faultType: {{http://schemas.oracle.com/bpel/extension}RuntimeFaultMessage}",
        "code": "{{http://docs.oasis-open.org/wsbpel/2.0/process/executable}selectionFailure}"
    }
}

Note that this happens randomly, i.e. sometimes the request is successful and sometimes it is not, and I always test by sending the same JSON object. I have tried restarting the WebLogic server and cleaning the MDS but it did not work. Attached is an image of the diagram of my BPEL process: https://i.postimg.cc/NMVH3MN1/capture2.png