I think I found a bug with playlists. When copying a album to a playlist it asks me if i want to add duplicates. I click no but when i go back the missing songs aren't there. So then i go back and copy all of them ignoring the duplicate message and low and behold they finely show up along with the duplicates. But can't delete the duplicates. I'm having problems where I try to delete duplicate songs out of playlists but the playlist won't let it delete. The only way i can fix it is to make a new playlist and add the songs to the new playlist. A duplicate playlist still has that problem btw. It's rather frustrating. this problem has happened on many occasions like now.
I'm using a Galaxy S7, a Galaxy Tab S 8.4, Poweramp, and Musicbee.