I have been experiencing this for a long time and just decided to come looking for a solution.
I did some searching these forums and only came up with old threads with no resolution.
I am running plex server on windows 10, and watch on my appletv.
I have only noticed this behavior when watching TV series.
I "Go to Show" for the series i want to watch, then select "Shuffle"
then it starts and episode as you would expect, but I keep seeing the same episodes very frequently. Its not ALWAYS the same order but there seem to be a dominant set of episodes that appear very frequently.
Without logging every episode in a spreadsheet as they are shuffled I dont think i could cite a pattern that I have noticed, just that I keep seeing the same set of episodes over and over.
any idea how i can get shuffle to actually shuffle all the episodes?
thanks