I was reorganizing my playlist library creating folders and drag-n-dropping playlists from the sidebar of the Spotify Linux client. Then after ~10 minutes (and 5/6 folders created) I couldn't start a drag action anymore. If I restart the client, sometimes I manage to move 1-2 playlists and then I have the same problem. Sometimes it doesn't even let me move one.
I'm on Debian 4.9.88, running version 220.127.116.118.g758ebd78 of the client.