In the past, I have had no problems with video. Recently, I have horrible performance. Also recently, for unknown reasons, I lost my connections to the servers and had to do the setups again. Also lost Plex which I use only for home movies.
Now, I get frequent “whirlybirds” on mp4’s.
We had guests last night and all settled into watching a movie and we all gave up after 1 minute of movie and 10 minutes of black screens with a twirling circle.
I’ll add one more thing, if you have the ability to change out the Ethernet cables even just temporarily give that a shot. I had an Ethernet cable go bad and not be a complete failure, just cut the speed to about 10% of what it was. That took forever to find and as soon as the new cable was in place everything was back to normal.