> For the complete documentation index, see [llms.txt](https://docs.coupler.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.coupler.io/sources/category/other/castor-edc/common-issues.md).

# Common Issues

## Connection issues

<details>

<summary>Authentication fails when connecting Castor EDC</summary>

This usually means your Client ID or Client Secret was entered incorrectly. Copy them directly from your Castor EDC account settings to avoid typos. Also confirm that API access is enabled for your account — some Castor EDC plans require you to explicitly activate API access.

</details>

<details>

<summary>Connection succeeds but returns no data</summary>

Check that your **start date** is not set too far in the future. If the start date is ahead of when your records were created, the filter will return an empty result. Try setting an earlier date or clearing the field entirely.

</details>

## Missing data

<details>

<summary>Audit trail data is incomplete or missing older records</summary>

The start date parameter filters audit records by timestamp. If you set a recent start date, older audit entries won't be included. To capture your full audit history, use the date picker to set the start date to the beginning of your study or organization's activity in Castor EDC.

</details>

<details>

<summary>Study visits or forms are missing for some studies</summary>

Castor EDC entities like study visits and forms are scoped to individual studies. If a study is archived, unpublished, or your API credentials don't have access to it, those records won't appear. Verify your user role has read access to all relevant studies in Castor EDC.

</details>

<details>

<summary>Study field dependencies or validations return empty results</summary>

These entities only contain data if your studies have conditional logic or validation rules configured. If you haven't set up dependencies or validations in Castor EDC, these entities will be empty by design.

</details>

## Permission errors

<details>

<summary>API returns a 403 Forbidden error</summary>

Your API credentials may not have sufficient permissions. In Castor EDC, API access is tied to user roles — ensure the account associated with your Client ID has at least read-level access to the studies and entities you're trying to export.

</details>

<details>

<summary>Can only see some studies, not all</summary>

Access to individual studies in Castor EDC is controlled per user. If your account is only assigned to certain studies, the API will only return those. Contact your Castor EDC organization admin to request access to additional studies.

</details>

## Data discrepancies

<details>

<summary>Study statistics don't match what I see in the Castor EDC dashboard</summary>

Statistics in Castor EDC may be calculated in real time from live data, while Coupler.io exports reflect a snapshot at the time of the last sync. Run the data flow again to get an up-to-date export. If numbers still differ, check whether filters (like site or date range) are applied in the Castor EDC dashboard but not in your export.

</details>

## Rate limits

<details>

<summary>Sync fails or times out on large exports</summary>

Castor EDC's API enforces rate limits that can affect large exports, particularly for audit trails on long-running studies. Use the start date parameter to limit the volume of data pulled per run. If you're exporting audit trails for a multi-year study, consider splitting exports by setting different start dates across multiple data flows.

</details>

{% hint style="warning" %}
If you repeatedly hit rate limits, avoid running multiple Castor EDC data flows simultaneously. Stagger them so they don't compete for API quota.
{% endhint %}


---

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