Attachments are not maintained when running the Project tool on a feature dataset with Maintain Attachments checked.

Workaround

• Run the Project tool as is. Then, click create/enable Attachments and use the Append tool. Refer to the following documentation for more information. https://support.esri.com/en/technical-article/000011569
• Move the feature class with attachments outside of the feature dataset. Then run the Project tool in ArcGIS Pro with Maintain Attachments checked.

Steps to Reproduce