I've ran into internal storage problems quite frequently, and ever so often I'll back up everything to my computer and do an internal storage wipe in twrp recovery. Then move all my files(pictures, ringtones, music, etc.) back over. That usually helps for me. You didn't state in the OP that you had custom recovery, but I'm just assuming you do. Chances are, if that 24x GB is/are important files, then you should be able to see them in your file manager. But since you can't, who knows what they are.
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