It seems that I rebooted while video transcodes were proceeding. Now I can see (from the UX, turning on the checkbox to show hidden videos) there are four videos that are transcoding.
Where do I go on the back end to diagnose / debug / fix?
No, it apparently did not!
Logging into the server and running top suggests that ffmpeg is consuming 100% of a CPU.
Ok going to chill and take a break while this thing churns.
Question: Does the road map include breaking transcoding off to a separate server / stack-of-servers? That would be nice for scaling.