If that is the case, it is almost certainly not running out of space for transcodes. In /var/log/jellyfin there should be FFMPEG log files. Check those out to see if they can give us insight into the problem.
Jellyfin 10.10.3 (Docker)
Ubuntu 24.04 LTS
Intel i3 12100
Intel Arc A380
OS drive - SK Hynix P41 1TB
Storage
3x WD Red Pro 6TB CMR in RAIDZ1 (JF Library)