I may have solved it. "Random" also looked for TV series which are deeply buried in multiple folders. Disabling "Shows" under the "Random Button Settings" via the "Advanced Settings (Jellyfin Enhanced)" menu (under the user icon top-right) did the trick.

#Jellyfin #JellyfinEnhanced #bug #softwarebug

Not sure if the latest #Jellyfin or the most recent #JellyfinEnhanced update which happened at around the same time, but when I request a random title, Jellyfin now sometimes shows a screenshot folder instead of the movie file. I assume it's caused by the folder's naming convention ("[NAME].mp4-MoviePrint-1").