Server will only use 80% of what is entered in the Upload Speed limit. 80% of 20 is 16
Though it applying that setting to a local stream is an issue. out side of this being a bug, only way off hand I can think is if you had some other IP in the LAN Networks"setting in Network because all other IPs or Netmasks will then be considered external. If you still have logs from that time of it happening it I would like to add it to a report so folks can try to reproduce.
the 80% is mentioned in this article but we probably need to mention it someplace else as well. : https://support.plex.tv/articles/227715247-server-settings-bandwidth-and-transcoding-limits/
