Wrap up code coming back null in analytics detail query

I’m pulling interaction details via the analytics API and hitting a snag with the wrap-up code. The query runs fine and returns data, but the wrapUpCode field is consistently null in the response payload. I’ve double-checked the UI and the agents are definitely selecting wrap-up codes during their wrap-up period. It’s not a data lag issue since I’m querying completed interactions from yesterday. Here’s the JSON payload I’m sending to the endpoint:

{
 "interval": "2023-10-01T00:00:00.000Z/2023-10-02T00:00:00.000Z",
 "groupings": [
 {
 "type": "wrapUpCode",
 "name": "wrapUpCode"
 }
 ],
 "aggregates": [
 {
 "type": "count"
 }
 ],
 "queryFilter": [
 {
 "type": "interactionType",
 "operator": "equals",
 "value": "voice"
 }
 ]
}

The response comes back with a 200 OK, but the bucket data for wrapUpCode is empty or shows null values instead of the actual codes like ‘Case Closed’ or ‘Callback’. Is this a known limitation of the detail query endpoint or am I missing a specific filter parameter to force the code to populate?