Yup pretty sure nothing should be reading from the mount, from the picture (Bandwhich hyperlink) you can see it's rclone not another process consuming 67Mbps of download bandwith, I'm expecting only upload of approx 4.5 Mbps
Nothing is using the rclone mount other than the upload, as you can see from the bandwhich screen grab there are a number of rclone processes all pulling 15+Mbps
Yes, and that means something is reading from the mount which is why rclone is downloading it.
It can be the rclone copy process (doubtful) or it can be something else. We will need the debug logs for both the copy and the mount to get any more info. RClone doesn't download anything without being asked for it.
What is your mount command and path? I don't think rclone can do server copy if the copy is done on a mounted partition (I might be wrong) also based on your rclone mount command, it could be rclone is caching some information when copy command is trying to read the files and explain the download.
Also, if you are copying from local to remote mounted using rclone, you are far better off copying directly to the remote and avoid the mounted partition. This will avoid a lot of overhead, avoid parallel uploads and just be far more efficient.
it should not be hard to figure out which process starts running at 03:00.
and to figure out which process is using the bandwidth.
did you check the Task Scheduler?
as i understand, rclone mount can do a server copy.
i would remove the cache backend, as it is almost never needed, buggy, and soon to be depreciated. https://rclone.org/cache/#status