I have a library of over 15,000 songs, nearly 500 artists, and hundreds of albums.
I just decommissioned an old Plex server which fed PlexAmp beautifully. Mood Radio, Genre Radio, and Library Radio (my favorite) worked without fail.
After building this new server, Genre radio is empty, Mood radio is empty, and Library radio plays the same seven or eight artists and 11 or 12 albums.
Both servers were on the same version of Plex (1.22.2.4282) but couldn’t behave more differently when it comes to how well (or not) PlexAmp cycles through my music library.