I even question if it is a DOS vector. So the thread crashes and then the system that controls the threads cleans it up and opens a new thread. Seems to be a trivial impact, unless it locks up the thread somehow.

Threads don't work that way. A fatal exception on any thread kills the process.

And the parent will spawn a new process. Unless the server is terribly poorly misconfigured. Edit; for what it’s worth I’ve run a server processing video with FFMPEG for 10 years now, and there’s just so many things that can make FFMPEG crash. All sorts of corrupted videos people upload. If your server doesn’t recovery gracefully from a crashed FFMPEG thread, that’s on you, not FFMPEG.