I seem to run into a similar problem since the last update of the dockerized Plex Server to version 1.18.9.2578 yesterday. In my case, it happened around 50 minutes into the movie, causing my entire NAS to lockup (which houses the docker container and transcode directory). After rebooting and restarting the container, it happened one more time again around the 50 minute mark (continuing the movie from where it crashed + 50 minutes). I have not set the server logs up, but I can see thousands of messages on the docker logs stating this:
decoder information: 249 and a few of these
decoder information: 102
I don’t remember seeing these numerous messages during transcoding before … then again I have not specifically looked for them recently