> ## Documentation Index
> Fetch the complete documentation index at: https://docs.unstructured.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Document processing issues

## Issues

When Unstructured tries to partition or chunk a document, you get one of the following error types:

* `TooManyPageFailuresException`
* `ControllerException`: For example, an error wrapping partitioning or chunking errors such as code `512`.

## Possible causes

* There are issues with the document's underlying content or structure.
* Unstructured encountered too many errors while processing individual pages or elements within a specific document, exceeding some internal failure threshold.
* The document is corrupted or malformed. This is especially the case for some complex PDFs.
* The document has a highly unusual underlying structure or has highly unusual content, which the specified partitioning model cannot handle.
* The document is encrypted or password-protected.
* Some underlying issues are causing page-level failures. This could sometimes be related to quotas if a per-page VLM is used.

## Possible solutions

* **Inspect the document**: Examine the specific document. Make sure it opens correctly, does not seem to look unusual, and does not appear to be corrupted or encrypted.
* **Test a simpler document**: Try processing a known-good, simple document of the same type, to see if the error is document-specific.
* **Check quotas (if VLM related)**: If the underlying errors mention quotas, see [Quota, billing, and rate limiting issues](/support/issues/quota-billing-rate-limiting).
* **Report the problematic document to Unstructured Support**: If the issue seems specific to an otherwise seemingly valid document, [report it to Unstructured Support](/support/request). If possible, provide the document for Unstructured to further investigate.

## Additional resources

To ask questions or get additional help with this issue, see [requesting support](/support/request).