iOS is download something from iCloud during the camera upload process
as many times reported by several users and discussed in the thread "Camera Upload on iOS constantly shutting off" the plex iOS app is downloading during the video upload process to the plex server something from the iCloud - it looks like buffering - before the actually upload.
The iCloud is totally disabled on my phone and no pictures or videos are stored in iCloud.
As I said, it seems that several users have this problem and in the mentioned thread, some screenshots are available.
What is plex downloading from the iCloud and why?