SOLVED: Completely unresponsive when scanning libraries

[toytown]

When Jellyfin hangs/becomes unresponsive, are there a boat load of ffmpeg processes running?

No. "jellyfin" process shows 100% cpu (1 core) and no ffmpeg (or any other processes) are launched.   I have all thumbnail extractions etc turned off.  The UI is unresponsive until cpu goes back down to 0%