I'm having trouble in connection with my Samsung Evo 128GB card as well. I have 5000 + songs on my sd-card, as I am writing reviews for a magazine, and I make playlists and naturally delete the songs I don't like. But when I delete a song, the phone spends 20-30 seconds performing the task. During this time the music player (GoneMAD Music Player) starts playing the next song on the list, but is not available until the task is done. Also, I try to enter new information on a song, it takes another 20-30 seconds from I press Save until the task is done. Also, when I use my player with the album cover on the screen and the song changes, it takes 20-30 seconds from the song changes until the new song info is showing on the screen. Now, I don't think the music player is the problem. I suspect it is communication with the sd-card. I haven't placed any apps on the card yet, but I would probably have the same issues you have if I did. Now, the phone is great, but these problems are really annoying, and I am actually considering returning the phone and go back to my S6.
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