A public survey with an image question submitted to ArcGIS Enterprise 10.8.1 by anonymous users fails to include the image attachment in the 'applyEdits' operation.
This is a known issue since ArcGIS Enterprise 10.7.1 and fixed in ArcGIS Enterprise 10.9. For more information, refer to https://support.esri.com/en/bugs/nimbus/QlVHLTAwMDEyNjk3NA==
解决办法
Define the submitters role: Add and Update Records or Add, Update and Delete Records.