When spawning a music disc and including the tag [!minecraft:jukebox_playable] using the /item or /give command, the ItemMeta of the item serializes with an "unhandled" parameter.

unhandled:H4sIAAAAAAAA/+NiYOBikFbMzcxLTS5KTCuxyirNTk3Kr4gvyEmsTEzKSWVgAABkGencIwAAAA==
removed:          
 - minecraft:jukebox_playable

This does not prevent the item from being deserialized correctly, as it maintains its lack of the "removed" functionality, however it prevents any copy of the item to be deserialized when a copy of the serialization is made (I.E copying the serialized ItemStack in config.yml to a different location and deserializing)

Steps to recreate: (x, y, and z are arbitrary inventory slots)
1 - spawn a disc that does not have the jukebox_playable tag and put it in the player's x slot
2 - make a plugin that will save the item in the player's x slot into the config.yml onDisable and load it back into the player's y slot onEnable 
2.1 - make the plugin save a blank ItemStack to be replaced with the music disk 
2.2 - copy the serialized ItemStack of the music disk to where the blank itemstack is
2.3 - make the plugin load the blank itemstack into the players z slot
3 - make the plugin serialize two ItemStacks, one that is the original, and one that is the copy
4 - the copy should be the same, but it no longer has the removed disc functionality