I have placed a help desk ticket into esri (Esri Case #03426294), on slow download of video attachments in ArcGIS Enterprise. Per the guy that handled my case he said that he could recreate it at Esri, so in theory it is not just me. I have an identical feature service, one at AGOL and another on ArcGIS Enterprise. When I download the video that is stored as an attachement on the point feature class I have very different response times:
- AGOL: 9 seconds
- Enterprise 1.5 to 2 minutes
The video is not that huge, maybe 25mb or so. As mentioned above he has the same response. I believes it to be a bug, with Enterprise but given that it does throw an error. It would be great if this was resolved in a future release.