Bandwidth errors

I host my PLEX server on a 2014 MacMini (Core i7, 16GB RAM, 2TB hard drive. Since the last update i keep getting a box saying “Playback Error” which says I don’t have sufficient bandwidth to play the Video. I have set Network Prefs to exclude the Mini from the network stream and should not have any problem playing any movie at original resolution. Works fine with all other devices on the LAN.
Don’t have a clue as to why. Seems to occur randomly with no common factor. Anyone have any thoughts? On the plus side the automatic resolution feature works fine but I sacrifice resolution and speed losses every time.

HELP!

I also get this error all the time even when playing streams locally. It’s as if Plex believes I’m streaming remotely, even though I’m on the local network.

Same problem how do we fix it?