My Music Playlist add song Problem

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http://androidforums.com – I'm using My Music on my Droid4 and I've been having a problem with the playlists. I'm trying to add more music to a specific playlist but when I add a new song it ends up replacing the one at the bottom of the list, so I end up having the same number of songs before trying to add a new one. (I'm stuck at 11 songs and I can't add any new one with out it replacing an old one) Curiously enough, if i delete the newly added song the old song it replaced is returned to the playlist. I made an account here solely to find any advice on this issue (General)