DuplicateKey Link between objects already exists error when creating Task via API call

Hi,

We have an issue while creating Project Tasks using Bulk Execute API endpoint lately.  The tasks are not being created and we receive DuplicateKey error, eg.

{
"errorCode": "DuplicateKey",
"message": "Link between objects already exists.\r\n",
"referenceId": "2mZVosLLjj130poA635tP6"
}

This error is thrown for about 50% of the calls, but it fails to mention which link it referees to, so we are unable to identify what could be causing it.

The example of the request is below:

{
"method": "POST",
"body": {
"entity": {
"StartDate": "2021-03-03T14:00:00.0000000Z",
"Parent": "/Project/10a5sed15b7nsy7s2uw6mqp4n177",
"Billable": false,
"Reportable": true,
"Work": {
"unit": "Hours",
"value": 0
},
"id": "/Task",
"Manager": "/User/c6b1d1f6-3696-4595-b391-61046fbad1e0",
"Name": "Non-Billable"
}
},
"url": "/data/createAndRetrieve/"
}

Thank you