Really annoying problem on plex web

Hello,

Since a few days i have a problem with plex player (app or web) on windows .
My server is on my desktop PC (Windows 10 up to date) and when i want to play something it’s really long and
case 1 : it stop with error “Playback Error” Shaka 1001
case 2 : the media play but at the lower quality even possible (i join some screenshot)

But on my ipad it work very well. On my laptop computer it work as well (W10 up to date too)

it seem like i haven’t the needed bandwith between my plex server and my pc.
But the problem is, my pc is also the plex server … so it’s a local playback !
can someone help me ?