How to fix the "States.ReferencePathConflict" error in AWS Step Functions?

I am trying to create a Step Function in AWS that iterates through a list of transactions, checks for the presence of a personal label, if transactions has 200 status code and a personal_label exists go to SuccessState, if FailState save each single transactions at postgres table
However, I am running into a "States.ReferencePathConflict" error and cannot proceed.

Input at TestPersonalClassifier

  {
  "statusCode": 200,
  "body": {
    "transactions": [
      {
        "customer_id": "****5135",
        "this_party_account_number": "****0600",
        "source_transaction_category": "DEBIT",
        "mcc": "0000",
        "transaction_amount": -20,
        "other_party_account_number": "****3214",
        "other_party_name": "bank life"
      },
      {
        "customer_id": "****5136",
        "this_party_account_number": "****7900",
        "source_transaction_category": "DEBIT",
        "mcc": "0000",
        "transaction_amount": -17.5,
        "other_party_account_number": "****9567",
        "other_party_name": "mt roskill liquor ce"
      }
    ]
  }
}

and I'm getting the correct output via TestPersonalClassifier lamda too which is

 {"statusCode": 200,
  "body": {
    "transactions": [
      {
        "customer_id": "****5135",
        "this_party_account_number": "************6600",
        "source_transaction_category": "DEBIT",
        "mcc": "0000",
        "transaction_amount": -20,
        "other_party_account_number": "*************4214",
        "other_party_name": "bank life",
        "personal_label": [
          {
            "label": "Insurance",
            "confidence": 1.0
          }
        ]
      },
      {
        "customer_id": "****5136",
        "this_party_account_number": "************7900",
        "source_transaction_category": "DEBIT",
        "mcc": "0000",
        "transaction_amount": -17.5,
        "other_party_account_number": "*************9567",
        "other_party_name": "mt roskill liquor ce",
        "personal_label": [
          {
            "label": "Entertainment",
            "confidence": 1.0
          }
        ]
      }
    ]
  }
}

What I need is simply if at lambda testPersonalClassifier output has statusCode= 200 and personal_label exits go to SuccessState else fail

When I run this Step Function, I get the following error:

States.ReferencePathConflict

    Unable to apply step "testPersonalClassifierOutput" to input 
   {"statusCode": 200,
  "body": {
    "transactions": [
      {
        "customer_id": "****5135",
        "this_party_account_number": "************6600",
        "source_transaction_category": "DEBIT",
        "mcc": "0000",
        "transaction_amount": -20,
        "other_party_account_number": "*************4214",
        "other_party_name": "bank life",
        "personal_label": [
          {
            "label": "Insurance",
            "confidence": 1.0
          }
        ]
      },
      {
        "customer_id": "****5136",
        "this_party_account_number": "************7900",
        "source_transaction_category": "DEBIT",
        "mcc": "0000",
        "transaction_amount": -17.5,
        "other_party_account_number": "*************9567",
        "other_party_name": "mt roskill liquor ce",
        "personal_label": [
          {
            "label": "Entertainment",
            "confidence": 1.0
          }
        ]
      }
    ]
  }
}

here is the Step Function

{
  "Comment": "Iterate through each transaction block and check if personal label exists",
  "StartAt": "TestPersonalClassifier",
  "States": {
    "TestPersonalClassifier": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:**********:function:testPersonalClassifier",
      "Next": "CheckPersonalLabelExistence"
    },
    "CheckPersonalLabelExistence": {
      "Type": "Map",
      "ItemsPath": "$.testPersonalClassifierOutput.body.transactions",
      "Iterator": {
        "StartAt": "CheckSingleTransactionPersonalLabel",
        "States": {
          "CheckSingleTransactionPersonalLabel": {
            "Type": "Choice",
            "Choices": [
              {
                "Variable": "$.personal_label",
                "IsPresent": true,
                "Next": "SuccessState"
              }
            ],
            "Default": "PostgresWithNoLabels"
          },
          "PostgresWithNoLabels": {
            "Type": "Task",
            "Resource": "arn:aws:lambda:*********:function:testSaveNoLabelAtPostgresDB",
            "ResultPath": "$.postgresOutput",
            "End": true
          },
          "SuccessState": {
            "Type": "Pass",
            "End": true
          }
        }
      },
      "Next": "Done"
    },
    "Done": {
      "Type": "Succeed"
    }
  }
}

It appears that your ItemsPath is incorrect. You specified $.testPersonalClassifierOutput.body.transactions but that does not exist in the output from your Lambda function. You need to change it to $.body.transactions.