Global Transfer API Shows Error ' The assignment number already exists..'

Hi All,

I try to do a employee global transfer use API

Change a Legal Employer

URL:

****.com/hcmRestApi/resources/11.13.18.05/workers/00020000000EACED00057708000110D9319C37A90000004AACED00057372000D6A6176612E73716C2E4461746514FA46683F3566970200007872000E6A6176612E7574696C2E44617465686A81014B597419030000787077080000019591F35C0078/child/workRelationships/300000002979758/action/changeLegalEmployer

Payload:

{  "actionCode" : "GLB_TRANSFER", 

"effectiveDate" : "2025-03-11",

  "legalEmployerName" : "****", 

"businessUnitName" : "****" },

It returns:

The assignment number already exists. Enter a unique assignment number. (PER-1530254)",        

"o:errorCode": "PER:::PER_EMCOR_ASG_INV_ASG_NUMBER"   

But in my payload, there is no information about assignment number and the legalEmployerName and businessUnitName are correct.

May I know why?

Thanks in advance!