This looks identical to my problem with remote streaming. Except mine only uploads at 6 mbps. I’m using windows server, same as you. It also affects all clients that try to play off of it, same as you. I’ll suggest something that helped me narrow it down to a windows + plex media server issue. Try putting PMS on a ubuntu 20.04 VM and see if the same upload problem exists. If it still exists, then the problem probably lies somewhere in your hardware/internet. As of right now, I’m running a ubuntu VM with plex installed. I mounted the media folders into the VM and managed to get quicksync to work on it (although it doesn’t say it’s HW transcoding, it is obviously HW transcoding because it behaves exactly as it did on my windows server). I’ve had zero remote streaming problems since.
While troubleshooting, I ran into a curious occurrence where when I reinstalled PMS on the machine and had my brother remote play, it played the file perfectly but once he restarted h is plex client, he had the 6mbps buffering. See the image below.
Link to my post with more details of my situation:
