PER_EMCOR_NO_FTE_ERR when updating worker category via PATCH assignment

Summary:

I'm trying to update a worker's category using Oracle HCM Cloud REST API with a PATCH request to the assignment endpoint, but I'm getting this error:

"o:errorDetails": [        { "detail": "You Can't Select This Position Because It Doesn't Have Enough Vacant FTE. (PER-1531659)",  "o:errorCode": "PER:::PER_EMCOR_NO_FTE_ERR"        }    ]

Content:

Current FTE value = 0 since the employee is on maternity leave

**Endpoint:**```

PATCH /hcmRestApi/resources/11.13.18.05/workers/{workersUniqID}/child/workRelationships/{PeriodOfServiceId}/child/assignments/{assignmentsUniqID}

Header

REST-Framework-Version:8

Effective-Of:RangeMode=UPDATE;RangeStartDate=2026-01-28

Payload

{ "ActionCode": "ASG_CHANGE", "WorkerCategory": "50"}

What I've checked:

• Position is active
• Worker category is supported on the target position