Got one few days ago and I can confirm its working perfectly fine. I just did software update on first boot, installed jellyfin and next thing Im watching a movie
this one also worked as advertised for the first day or two and started glitching by day three. I'd a appreciate if you could ping back in a couple of days whether it's still working.
I was reading other comments as well. You can also disable transcoding on the client side, the video will not play at all if transcoding is required. Also try disabling subtitles, sometimes subtitles require transcoding for some reason (don't know why tho).
What's you network setup? Is there any chance that it's connecting through he Internet instead of locally? For example: JF proxies through a VPS, and you're connected to the VPS address instead of the local address of the server?