Web Service Endpoints API Create Record for custom DAC in Acumatica.

Hi everyone,
I’m currently working with Acumatica and trying to expose a custom table via REST API. I created a custom API entity and endpoint, but the API Create Record doesn't work.

I'm using 
  Post {{url}}/entity/webOrderTaxComparison/22.200.001/webOrderTaxComparison/Save
  Body:
  
  {
  "Entity": {
        "WebOrderTaxComparisonID": { "value": 2 },
        "WebOrderID": { "value": "WEB006" },
        "AcuOrderID": { "value": "ACB006" },
        "AcuTaxTotal": { "value": 95.50 },
        "WebTaxTotal": { "value": 95.75 }
    }
}

  
  or 
  
  Put {{url}}/entity/webOrderTaxComparison/22.200.001/webOrderTaxComparison
  Body:
  {
        "WebOrderTaxComparisonID": { "value": 2 },
        "WebOrderID": { "value": "WEB006" },
        "AcuOrderID": { "value": "ACB006" },
        "AcuTaxTotal": { "value": 95.50 },
        "WebTaxTotal": { "value": 95.75 }
    }
  
  response issue is:
  "message": "An error has occurred.",
    "exceptionMessage": "Sequence contains more than one matching element",

However, I delete "webordertaxcomParisonid": {"Value": 2},
  Then do not Create Record it has the problem:
  
  "message": "An error has occurred.",
    "exceptionMessage": "An item with the same key has already been added.",

My custom graph:

And the DAC:

My custom screen VX101010

A custom REST API endpoint,

Since I created a separate custom API endpoint and manually mapped the fields, is there anything else I need to do for Acumatica to API Create Record works ?

  Any tips would be greatly appreciated!