I don't know if your field operators are working in the same area as one another, as well as on different platforms - apple vs. android - so this might not be the solution you're looking for, but it also might help you between now and getting an answer from ESRI.
After having similar attachment/update-related issues with our fleet of Androids (along with other connectivity-related issues), we decided to take our collector maps offline (w the .tpk basemap downloaded right onto the device), and operate in a collect-sync workflow. The attachments store right on the device until sync, and we found that sending updates in this manner was 100% less buggy (especially when syncing is done with a wifi-connection vs. 3/4G).
Hope this helps!
Just for some clarity (before raising the issue with tech support)...
Can anyone upload a photo with Android and Collector 10.3.7 in online mode?
I can see in Fiddler the call to upload the features:
though nothing to send in the attachment.
Our environment all works ok with iOS devices.
I can't do a trace on the iOS device as Fiddler causes an error:
The 'Proxy-Connection' header must be modified using the appropriate property or method. Parameter name: name
I think the iOS Fiddler error is just a distraction for me right now
Just updated to android collector 10.4.0 and attachments/photos still fail to upload in online mode, yet no problem when collecting data in offline mode and then sync features.
jachilles We are having the same problem with Android devices not being able to upload attachments. Our Apple devices are able to with no problems. Did you ever find a solution for this? We are using Collector version 10.4.2 build 1026 Thanks!