Custom Object Service Intermittent 500 From Multiple Instance Reference ID
The error Internal Server Error. Status=500 content={"error":"internal error","caseId":"2c36567b-49d7-4fca-86ce-f3c88ade2156"}
What it means
An outbound Studio integration using a workday-out-rest transport to update a custom object intermittently returns a generic HTTP 500 with a caseId instead of a specific validation message. The custom object's field setup, not the integration code, is usually the cause.
Troubleshooting
- Note whether the failure is truly intermittent (some records succeed, others fail with 500) rather than consistent, since a consistent 500 usually points to a different root cause such as auth or a malformed payload.
- Check the custom object's field definitions for any field configured with a Multiple Instance Reference ID.
- Confirm whether Allow Multiple Instances is actually enabled for that field. A Reference ID present on a field that does not allow multiple instances creates an inconsistent internal state that can surface as this 500 only when fields are updated out of order.
- Reproduce by updating the object's fields in a different order, such as populating the first field before the second, to see if the error disappears, confirming the field ordering theory.
- Treat the caseId in the response as Workday internal reference, not a code you can look up yourself; fixing the field configuration resolves it faster than opening a support case.
⚡ Quick fix
Reorder the integration so it populates the custom object's fields in the same sequence they would be filled in manually, or update all fields in a single request instead of sequential PUT calls.
✓ Permanent fix
Remove the Multiple Instance Reference ID from any field where Allow Multiple Instances is not actually enabled, or build the custom object without a multiple instance reference field when the business object does not need one.
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