From time to time, I've had Field Map users have reported an error message that their attachment failed to upload. I've verified that the geometry and attribution updates have made it back to the SDE database and that their photo size is set to medium. The ArcGIS Server Logs, as far as I can see, only log successful attachment uploads. I'm not seeing anything pertaining to failures.
I'm not sure what other steps I can take to troubleshoot the matter other than making sure they have better data coverage at the time of upload or having them continue to hit resubmit until the upload is successful.
Any ideas?