The "Change task assignees" REST API call is not working.

Following are the details:
End-point: xxx.yyy.com/.../changeAssignees
Payload: [{"id":6457980,"assignedRoleIds":[8073],"taskStepIds":[243608648]}]

Response:
{
"status": "ERROR",
"response": [
{
"status": "ERROR",
"errors": [
{
"code": 404,
"type": "NOT_FOUND",
"message": "Resource TASK_STEP ([243608648]) not found."
}
],
"id": 6457980
}
]
}

Note: The TASK_STEP_ID 243608648 exists in the database for the TASK 6457980

Relevant Database record from tasksteps table:
243608648 6457980 304915 1 02-09-25 2 Linguistic Review Human

I referred following World Server REST API document
docs.rws.com/.../change-task-assignees-645027