Music app won't stay put

I use two monitors. I carefully arrange apps I keep open on each to suit my preference. All stay put, except the Apple Music app. Whenever I wake the computer (iMac, running macOS Catalina 10.5.7) from sleep, everything stays where I arranged it except the Apple Music Mini Player, which always moves to the primary monitor (which I try to keep clean for general purposes).

What gives? This is obviously not a big problem - I can just drag it over to the secondary monitor. It just seems so stupid. I quietly curse Apple every time.