Unexpected Error when attempting to Auto-Label documents in Custom Task for Content Understanding

Hi ,

Thanks for reaching out to Microsoft Q&A.

This is typically a generic backend failure with poor surfacing of diagnostics, not a user-side validation error. In Content Understanding custom tasks, “Unexpected Error” during auto-labeling usually comes from one of these:

• Service side issue/transient failure - retry often works
• Dataset or file format issue - unsupported encoding, corrupt files, or size limits
• Label schema mismatch - recent changes to schema not synced with existing documents
• Permission/RBAC issue - especially if using shared workspace or different identity
• Region or capacity constraints - some features are still limited/preview-backed

What to do quickly?

1. Retry with a small known good document (rules out data issues)

Check if schema was modified after uploading documents

1. Recreate a new custom task and test auto labeling there
2. Validate file types, size, encoding (UTF8 preferred)
3. Check azure status + region availability

If consistent, raise a support ticket with operation timestamp + resource ID (needed since logs are not exposed)

Bottom line: if it fails even with a fresh task + simple document, it is almost certainly a backend issue or preview limitation, not your configuration.

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