Playlists won't stay in folder

[iolarah]

Premium, Canada. Multiple devices: MacBook Pro 2018 (desktop app, on Mojave), HP Elitebook (x2, one running web app, one running desktop app, both Win10), Pixel 2 (mobile app, on Android 10)

Over the last two weeks, I've noticed that all the playlists I have in one folder will not stay there. Prior to this, they were all staying put. I started using a MacBook and noticed that the contents of this folder were all in the root directory instead. I moved them back, and when I looked at them again in the web app, they were out in the root again. I put them back in, and later when I went to the mobile app, a couple were in but the rest were out. 

I can't tell if there's any consistency to the way they behave from system to system, platform to platform, but it's really irritating. Has anyone else encountered this, and if so, what's the fix?