Unable to export a large hosted feature service with attachments to a file geodatabase from a REST endpoint

Description

When downloading a large hosted feature service with attachments from ArcGIS Online to a file geodatabase, a known issue may occur that results in an error, or in missing feature layer attachments. One possible workaround for the issue is documented in the following article, Download and extract a hosted feature layer with attachments as a file geodatabase in ArcGIS Online, which suggests creating a replica from the REST endpoint of the hosted feature service and downloading it as a zipped file geodatabase.

In some instances, attempting to export the hosted feature service with attachments from the REST endpoint fails, or results in missing feature layer attachments.

Cause

The following are two possible causes of the issue:

• The hosted feature service is too large. This is a known issue.
• The hosted feature service contains corrupt feature attachments.

Solution or Workaround

As a workaround, add the hosted feature service to ArcGIS Pro and use the Feature Class To Feature Class or Export Features tool to export the hosted feature service to a file geodatabase.

Note:
The ability to maintain attachments of features is supported by the Maintain Attachments environment, which was introduced in ArcGIS Pro 1.3. The Maintain Attachments environment setting allows enabling and disabling the transfer of attachments to the output table or feature class.

1. Launch ArcGIS Pro, and sign in to ArcGIS Online.
2. Add the hosted feature service to the map.
3. Click the Analysis tab, and click Tools in the Geoprocessing group.
4. In the Geoprocessing dialog box,search for and select Feature Class to Feature Class or Export Features.

Note: 
The Feature Class To Feature Class tool was deprecated in ArcGIS Pro 3.2, and has been replaced by the Export Features tool, which provides the same functionality. 

5. In the Feature Class to Feature Class or Export Features pane, configure the parameters and ensure Maintain Attachments check box on the Environments tab.
6. Click Run.

The exported feature class is stored in the file geodatabase specified in Step 5, containing the feature attachments. Refer to the following document for steps to view or open the feature attachments in ArcGIS Pro: Open an attachment. The figure below is an example of the exported feature containing the attachments.