WFM API 409 on Shift Swap Validation

{
 "errors": [
 {
 "code": 409,
 "message": "Conflict with existing schedule constraint",
 "parameter": "shiftSwapId"
 }
 ]
}

The /api/v2/wfm/schedules/shiftswaps endpoint is rejecting valid swap requests for Chicago agents during the Tuesday publish window. The UI shows availability, but the API blocks the trade citing a constraint violation that does not exist in the schedule rules. How do I bypass or debug this specific 409 conflict without manually overriding the schedule?