Plex stuttering at 4k streaming

Hi there, i was wondering if anyone else has had stuttering while streaming 4k? i am on a Vampire box, because i wanted to stream 4k Media!

my home connection is 1/1Gbit!

for some reason, while using Plex for windows ( https://www.plex.tv/media-server-downloads/#plex-app ) i get very bad stutter! like.. movie goes all slowmotion on me! its not 100% of the time, it just.. its allot! and very often!

i am wondering, has anyone else had this happen? and if so, how does one go towards solving this?