Motion settings on the camera? Some user accessing the camera to view footage? Is it a one-time occurance or does it repeat every day/hour? Settings identical between this camera and another one nearby? Have you tried reset/restart the camera?
Motion sensor is on as I thought that was the best option to use. Users are not viewing if they are its on same subnet so shouldn't be any upload of data then. I do see it daily sometimes its different cameras, like yesterday there was one camera that uploaded 4.3gig that day. I do have all cameras set exact same.
When they are accessing the cameras do they have the cloud icon or the tick?
At my home due to some poor configuration of the ISP supplied router I cannot access the 'live' stream locally unless I manually change the viewing PC's DNS to Google's servers. Therefore every view triggers upload traffic.