Are you streaming to a Chromecast, by any chance? Or a older Galaxy device?
The 4k Chromecast with Google TV does not support AV1, but the 1080p version does. Jellyfin tried Direct Playing AV1 files, which obviously went poorly.

I run the same CPU in my NUC as you do, and all data is on a NAS shared with NFS. It’s been absolutely bulletproof for about a year, so I’m confident you should be able to make this work.

Any other containers running at the same time?
No cooling issues?

Just asking because mine dropped massively in temp when repasted.