As pictured, when in cake boss hair becomes transparent. I have confirmed that the same issue happens with the Party Hat in the Cash Shop preview window. I don't know if this bug is specific to this hairstyle but this is the Sweet Lily Hair from female hairstyles #4.
Update, I have tested Connie hair and Olive hair as well and the issue doesn't exist, so likely this is just a Sweet Lily Hair problem. Have replicated the problem on different characters with the same hair.
